Many commentators have found this denouement lacking in credibility, but Shakespeare's purpose was symbolic, and realism should not be expected. The Duke controls the outcome and thus fulfils the ruler's proper role in the play's scheme of things. He offers the mercy of God to the deserving and undeserving alike. It is he who recognizes in Barnadine, the vicious murderer, a mere 'creature unprepar'd' (4.3.66), and he forgives LUCIO his slanders, despite the insult to both his personal pride and his authority. Most important, he proves susceptible to the pleas of Mariana and Isabella for mercy towards the villainous Angelo. Finally, though he has earlier claimed immunity from 'the dribbling dart of love' (1.3.2), he proposes marriage to Isabella. In striking contrast to the negative attitudes of both Angelo and Isabella, early in the play, the Duke underscores Shakespeare's belief in the happy marriages that traditionally close a Comedy.

Once Isabella's refusal to meet Angelo's demand has left Claudio facing death, in 3.1, the Duke takes over the play, and Angelo is not seen very much until his conviction and reprieve in 5.1. Because Shakespeare wished to employ the happy ending of traditional COMEDY, he was compelled to abandon the psychological portrait of Angelo, though the fallen deputy remains stern at the close, seeking death rather than marriage and forgiveness. Whether the villain's reduced importance is seen as a flaw in the play or simply as a strategy in the service of a non-realistic end depends on one's view of Measure for Measure, but in any case Angelo remains a powerful creation.

Escalus is a subordinate to the Duke of Vienna. Escalus is a respected elder—the Duke praises the 'art and practice' of 'Old Escalus' (1.1.12, 45). He is appointed Angelo’s second-in-command in the Duke's absence, and serves as his foil in the play. He consistently advocates mercy for Claudio, in opposition to Angelo's determination to execute the young man for fornication.  Though his pleas are dismissed, he continues to defend the ideal of justice tempered with mercy. On the other hand, in the comical trial scene of 2.1 Escalus represents the opposite failing of government in being too lax when he releases the pander Pompey with a warning—one for which the pimp has no respect.  This produces the anomaly that a hardened promoter of prostitution goes unpunished while the honorable Claudio remains under sentence of death. Escalus contrasts with Angelo in another respect: he is true to his duty while the Duke's deputy is corrupted by his lust for Isabella. Though he disagrees with Angelo's severity towards Claudio, he limits his resistance to argument and makes no effort to forestall the decision of his superior officer. The Duke recognizes his devotion to duty at the play's close. Escalus' chief function is to serve as a symbol of both dutiful submission and kindness.

Claudio's situation is a result of the Duke's lax regime in Vienna. Despite his aristocratic upbringing, the young man is familiar with the bordello world of Lucio, Pompey, and Mistress Overdone, from whom we first learn of his plight, in 1.2. We recognize the stereotype of an immature young man in bad company, and we are not surprised that his ascetic sister is disappointed in him when his fear of death overcomes his sense of nobility. The moving passage in which he begs her to accommodate Angelo begins, 'to die, and go we know not where' (3.1.117). His reaction is touchingly human and we do not share Isabella's hysterical condemnation; the episode helps us realize that she is, in her way, as extreme as Angelo. Claudio's moral character is favorably compared with Angelo's in the contrast between his loving relationship with Juliet and Angelo's desertion of Mariana. 

We first see Lucio in 1.2, jesting lewdly about venereal disease with his friends (see Gentlemen. A customer of the bordello run by Mistress Overdone and Pompey, Lucio represents the degenerate life that has flourished in Vienna because of the Duke's lax regime. He is not without good qualities, however.   In standing by Isabella, in 2.2 and 2.4, he seems a positive figure, but beginning in 3.2 he takes on another aspect. He flippantly refuses to help Pompey avoid imprisonment, and Mistress Overdone declares that he has informed on her; these episodes make us realize that Lucio's Vienna is an ugly one. In 3.2 and 4.3 Lucio amuses himself by making up the libelous stories about the Duke for which he is punished in 5.1. He does not realize that the 'friar' with whom he converses is the disguised ruler himself.  While Lucio's slanderous lies are plainly malicious, he seems funny, not evil, to modern sensibilities. But abuse of a ruler—believed to be appointed by God to maintain order in society—was a much more serious matter in Shakespeare's day than in our own, and Lucio's offence, although comical, is decidedly criminal. 17th-century audiences would not have been surprised by the severity of the Duke's proposed punishment: 'Let him be whipp'd and hang'd' (5.1.511).  Nevertheless, Lucio remains wittily uncompromising at the end. This testifies to Shakespeare's sympathy with the rebellious individual, even in a play which stresses the importance of authority and the values of society at large.

Gentleman are the friends of Lucio. The Gentlemen appear briefly in 1.2 where they help establish the ambience of the play's subplot, the atmosphere of  vice and degradation amid good spirits that characterizes the underworld of Vienna. They are soldiers who callously regret the prospects of peace and go on to jest about venereal disease, especially when Mistress Overdone appears. The Gentlemen have no distinct personalities and are not distinguishable from each other. After this brief scene they disappear from the play.

Provost is the warden of the prison in which Claudio is jailed. From his first appearance-when he exposes Claudio to public humiliation at the orders of Angelo but declares ‘I do it not in evil disposition' (1.2.110)—we see the Provost to be a kind and honorable man. He pleads with Angelo to be merciful towards Claudio and clearly presents a sensible view of the young man's offence thereby emphasizing Angelo's extremism.  Nevertheless, the Provost is prepared to do the duty of his office and oversee the young man's execution.  In this way, he offers a contrast to the moral laxity that created the problem in the first place.  In a telling episode the Provost demonstrates Shakespeare s position that social order has a high value. This clearly sympathetic character who obviously favors mercy for Claudio nevertheless resists the attempts of the disguised Duke to find a way to save the young man until the Duke produces letters that reveal his authority. Then, supported by the knowledge that he will not be opposing the ruler-Shakespeare and his original audiences believed that rulers were appointed by God—he can enthusiastically help. 

The Friar is named Thomas in the stage direction at the beginning of 1.3, but the name is never used elsewhere, and in a later appearance he is named Peter.  Shakespeare—who made such minor slips throughout the plays—apparently gave the Friar a name when he first created him, but then forgot about it before writing Act 4 where he gave him another one. The earliest text of the play, that of the Folio, was printed from a transcription of Shakespeare's manuscript, and his original note was erroneously included.

Justice is a magistrate of Vienna. The Justice appears only in 2.1, speaking three lines to his superior, Escalus. This brief exchange serves to remind the audience of the condemned Claudio after the diversion of the long comic trial of Pompey. The Justice and Escalus depart together at the close of the scene.  Some scholars believe that the Justice's absence elsewhere in the play is evidence that it was considerably revised. Another theory supports only a tiny revision, holding that the Justice's lines had originally been written for the Provost, but that in production they had been reassigned. Normal stage practice in Shakespeare's day frowned on an immediate re-entrance after an exit, and since the Provost opens the next scene, he could not close this one by leaving with Escalus. So, possibly, a new character was invented by Shakespeare or someone else. As a matter of economy, the Justice is often cut from modern productions and his lines eliminated or given to the Provost.

Varrius is a follower of the Duke of Vienna. Varrius is addressed by the Duke in 4.5 and is mentioned in the stage direction opening 5.1, the Duke's formal entry to Vienna, but he does not speak, nor does he appear in the list of characters in the first published text of the play, in the First Folio. Some scholars believe that this is evidence that the play had been cut before it was published. On the other hand, Varrius may be seen as a representative of the Duke's entourage whose tiny part in 4.5 prepares the audience to perceive the Duke's return in 5.1 as a ceremonious occasion.

Elbow is a comic constable of Vienna. Elbow brings Pompey to court, in 2.1, and attempts to prosecute Froth for an unspecified insult to his, Elbow's, wife. However, with his comical mispronunciations and unconscious double meanings he is a stereotypical Clown, and he cannot make a sensible accusation. He is foiled by Pompey's humorous evasions, which result in the dismissal of the case. The episode serves as comic relief from the increasingly tense main plot. It also illustrates vividly the SUB-PLOT'S world of petty vice and crime, standing in striking contrast with the more rigid world of the Duke, Angelo, and Isabella. In 3.2 Elbow has the satisfaction of bringing Pompey to prison, though his triumph is not so humorous as his defeat. Compared to his better-known predecessor Dogberry, Elbow is a less successful version of an ancient character type—the bumbling, foolish constable. His is a familiar figure in traditional English drama: in 2.1.169, Escalus compares Elbow and Pompey to Justice and Iniquity, characters in a Morality Play.

As Escalus observes in 2.1.169, Pompey resembles Iniquity, a character from the medieval Morality Play. He represents a type that was well known, the clownish criminal (he is designated as a Clown throughout the Folio text of the play). A comic subplot featuring a madam and her servant was found by Shakespeare in a principal source for Measure for Measure, George Whetstone’s Promos and Cassandra (1578), and its appeal was surely immediate for the creator of Falstaff. Pompey's preposterous name was  Shakespeare's invention: an ancient Roman hero, Pompey the Great, is provided with a surname that is slang for buttocks.

Abhorson is an executioner. Abhorson appears in 4.2, where he undertakes to train the pimp Pompey as his assistant, and in 4.3, where he and Pompey summon the condemned criminal Barnadine to be executed, only to be comically frustrated by the victim's refusal to cooperate.  Abhorson is part of the comic subplot-in 4.2 he drolly claims the status of 'mystery' for his profession—but he serves chiefly to help create the ominous atmosphere of the prison. Abhorson's name, which suggests both the verb 'abhor' and the insulting noun 'whoreson', serves the same two purposes. It conveys clearly the repellent aspects of the man's profession, thereby reinforcing the atmosphere of impending doom that has been established earlier in the play, even as its absurdity helps defuse that tension.

Barnardine is a condemned criminal whose undeserved pardon epitomizes the play's theme of unqualified mercy. Barnardine is a comical brute who is 'drunk many times a day, if not many days entirely drunk' (4.2.147-148).  He declares he will not come forward to be executed on the day appointed—when he is to substitute for Claudio—because he has 'been drinking hard all night, and [needs] more time to prepare. . .' (4.3.52-53). The Duke postpones the execution, saying that under the circumstances it could only send the victim to instant damnation, a responsibility the Duke will not take. In 5.1 the ruler pardons Barnardine and remands him into the custody of the Friar as part of the mercy and forgiveness of the play's denouement.  Barnardine is funny in his stubborn refusal to be killed and helps provide relief from the oppressiveness of the prison, where much of the middle of the play is set. Yet he is a callous murderer 'unfit to live or die' (4.3.63). Although Barnardine is specifically designated as a proper subject for execution, he is pardoned as part of the play's final conciliation; his evilness then highlights the magnanimity of the Duke's mercy.

While the play's ending often seems arbitrary to modern readers, its convenient resolution of the impending tragedy was not only perfectly acceptable in Shakespeare's day, it was highly satisfying: the triumph of good, in a clear and traditional manner, gratified the sentimental feelings of audiences. While Isabella is somewhat diminished as a character by her symbolic quality in the play's denouement, she is nonetheless sufficiently well developed to rank among Shakespeare's most interesting heroines.

No hint of Mariana is to be found in Shakespeare's sources for Measure/or Measure, and the character has particular importance as she is an invention of the playwright that changes the nature of his story in a significant manner. In all of the sources for the play, the Angelo figure successfully extorts sex from the Isabella figure, and then, when exposed, he is forced to marry her. However, in Shakespeare's rendering of the tale, Isabella and Angelo have effectively been presented as intense figures whose opposing psychological strengths make such a union impossible to contemplate. Mariana therefore replaces Isabella. The bed trick, an ancient comedic device that Shakespeare also used in All's Well, accomplishes this end. Isabella is preserved as the virtuous counterpart to Angelo's corruption, and Mariana can influence her towards forgiveness as her rigidity relaxes. The device may seem arbitrary to modern readers—like a deus ex machina, it disposes of the impending tragedy with ease and convenience—but in Shakespeare's day this conclusion was not only perfectly acceptable, it was highly gratifying to the audience's sentimental feelings.

Juliet is the pregnant fiancee of Claudio. Claudio's death sentence for having illicit sex with Juliet is the central element of the play's plot, but the young woman is nevertheless a shadowy and undeveloped character.  She speaks in only one of the three scenes in which she appears (2.3), and though she is touching in her combination of repentance and love, she remains a minor figure.  The role of Juliet is small, and this has suggested to some scholars that the play was at some point extensively revised—by Shakespeare or someone else—and her role was awkwardly cut. However, other commentators feel that her function as a pathetic victim is fully realized by her mere presence, and any enlargement of her role would be distracting.

Nun Minor is a member of the convent that Isabella intends to join. The Nun appears only briefly, in 1.4, when she listens to Isabella's complaint that the restrictions imposed on the nuns seem insufficient. When she hears Lucio’s voice she asks Isabella to receive him, for she may not speak to a man except in the presence of the prioress and then only while hiding her face; if showing her face, she must be quiet. Having established these regulations for the audience, the Nun disappears from the play; except for a momentary disturbance at the approach of Lucio, she displays only the quiet of the stereotypical nun. The episode illustrates Isabella's extremism, as we see that she is determined to adopt a sterner rule of withdrawal than that required of the Nun.  The Nun is named Francisca (or Francesca) in the stage direction at the beginning of 1.4, but the name is not used thereafter. Scholars believe that Shakespeare named his character when he created her but then never used the name. Its survival in the earliest published text, the First Folio (1623), is viewed as evidence that the printed text came from Shakespeare's manuscript.

Mistress is the keeper of a bordello in Vienna. Mistress Overdone's principal role is as a stereotypical member of Vienna's underworld, which stands in contrast to the world of the major characters. Her servant Pompey is the most important figure of this comic subplot.  Mistress Overdone is a familiar figure to Lucio and his friends; her entrance inspires each Gentleman to jest about venereal disease, establishing the bawdy, depraved tone of the sub-plot. She also introduces a major element of the main plot when she first appears in 1.2 and tells of the prosecution of Claudio. She is comically presented as a typical innkeeper, worried about business, though this also includes worrying about the government's attempts to fight prostitution.  When she is imprisoned in 3.2 she complains that she has been informed against by Lucio. This reminds us that her world of petty vice is not truly a comic one.  A comic sub-plot featuring a bordello madam and her servant was found by Shakespeare in one of the sources for Measure/or Measure, George Whetstone’s Promos and Cassandra (1578). However, Shakespeare invented the preposterous names they bear in his play, Mistress Overdone's name reflects her status as a veteran of her profession.

Servant is an attendant to Angelo. The Servant receives the Provost in 2.2 and announces Isabella’s arrival in 2.4. His presence reminds us of Angelo's importance and power.