Arturo Ui is a violent Chicago gangster seeking to seize control of the city's vegetable trade. Frustrated by his lack of current influence and poor public image, he actively looks for opportunities to expand his protection racket. He is highly ambitious and deeply paranoid, relying heavily on a carefully crafted public persona to mask his private insecurities.

Ernesto Roma serves as Arturo Ui's oldest friend and most dedicated lieutenant. Unlike the other gangsters who vie strictly for personal financial gain, Roma genuinely supports Ui and believes in the effectiveness of violent intimidation. He takes immense pride in his status within the gang and constantly watches for potential threats to his boss.

Old Dogsborough is a highly respected elderly politician in Chicago who previously belonged to the Cauliflower Trust. He enjoys an immaculate public reputation that represents a bygone era of political innocence. He finds himself targeted by his former business associates, who need his respectable image to secure a massive government loan.

Bowl is the former chief accountant for Sheet's dockyard business. Following the transfer of the dockyards to Old Dogsborough, he loses his job and seeks immediate revenge. He possesses critical knowledge about the financial corruption surrounding the dockyard deal and is willing to share it with the criminal underworld to punish his former employer.

Giri is one of Arturo Ui's top lieutenants and a ruthless enforcer for the gang. He uses a jovial, clownish demeanor to obscure his violent actions and true nature. He takes immense pleasure in intimidation and frequently wears the hats of his victims as a macabre public warning to those who might oppose him.

Givola is another of Arturo Ui's key lieutenants, operating as a scammer and chief propagandist. He runs a local flower shop that serves as a front for his criminal activities. He excels at manipulating public perception, fabricating documents, and frequently speaks in rhyming couplets during tense negotiations.

Clark is a director of the Cauliflower Trust who actively works to align the vegetable merchants' interests with Arturo Ui's protection racket. He serves as a primary bridge between the respectable business world and the criminal underworld, consistently prioritizing profits over ethical concerns.

Butcher is a director of the Cauliflower Trust who devises the scheme to use Old Dogsborough's pristine reputation to secure a government loan. He acts as a smooth talker, convincing others to participate in corrupt financial deals under the guise of civic duty and corporate necessity.

Flake is a prominent director of the Cauliflower Trust who works closely with Butcher to execute the dockyard corruption scheme. He frequently complains about the gangsters infesting the city but ultimately relies on underhanded tactics to save his struggling business.

Sheet is an independent businessman who owns a shipping company and the local dockyards. He refuses to bow to the Cauliflower Trust's demands to sell his property at a heavy discount, making him a major obstacle to their government loan scheme.

O'Casey is a city clerk and investigator dedicated to uncovering the truth behind the Cauliflower Trust's financial irregularities. He stands as one of the few officials willing to challenge Old Dogsborough and Arturo Ui publicly in a court of law, attempting to uphold justice in a rapidly deteriorating system.

Fish is an innocent man framed by Arturo Ui's gang for the burning of a greengrocer's warehouse. During his trial, he appears largely unable to speak properly and is heavily drugged by a corrupt court doctor, preventing him from adequately defending himself against Giri's false accusations.

Ignatius Dullfoot is a prominent press baron in the neighboring town of Cicero. He expresses deep wariness toward Arturo Ui's violent methods and attempts to resist the Chicago gangster's expansion into his local market, preferring to maintain an independent economy.

Betty Dullfoot manages the vegetable trade in the town of Cicero. She works alongside her husband to maintain their local business empire but soon finds herself politically isolated and heavily pressured to merge her operations with the Cauliflower Trust under Arturo Ui's protection scheme.

Mahoney is a down-at-heel, drunken actor hired to give Arturo Ui lessons in pronunciation and physical presentation. He teaches the gangster how to project authority, walk with purpose, and appeal to common people using classical theatrical techniques.

Dockdaisy is a woman who frequently associates with criminals in Chicago's taverns. She is later manipulated by Givola to appear in public under a false identity, providing heavily rehearsed testimony to support the gang's legal and public relations interests.

Hook is an independent greengrocer who attempts to resist Arturo Ui's protection racket. After his warehouse is burned down by the gang, he is severely beaten and intimidated into altering his testimony on the witness stand to protect the perpetrators.

Mulberry is a director of the Cauliflower Trust. While initially supportive of using the gang's influence to boost business, he eventually grows deeply disgusted by the brutality of Arturo Ui's methods and regrets the Trust's alliance with violent criminals.

Young Dogsborough is Old Dogsborough's son. He assists his father with daily tasks and serves as a primary, emotional reason why his father accepts the Cauliflower Trust's corrupt financial gifts, hoping to secure his family's future comfort.

Caruther is a director of the Cauliflower Trust who initially expresses clear disdain for Arturo Ui's violent tactics. His early resistance makes him a direct target of the gang's intimidation efforts when his delivery truck is attacked.

Young Inna is an enforcer who works directly under Ernesto Roma. He prepares for what he believes is an upcoming gang war, remaining fiercely loyal to Roma's faction within Arturo Ui's larger organization.

The Announcer serves as the master of ceremonies for the play itself. He speaks directly to the audience, introduces the main characters, and explicitly outlines the story's events to ensure observers focus on the political message rather than narrative surprises.