The Baccano! light novel and anime series feature an extensive ensemble cast of characters created by Ryohgo Narita and illustrated by Katsumi Enami. Largely set in a fictional United States, the series tells many loosely connected stories about people brought together by immortality and is often told from multiple points of view. The events occur throughout many decades; most take place during the Prohibition-era while others are set in the 18th century and the first decade of the 21st century.

The cast is made up of many seemingly unconnected characters and at least twenty main characters, Click "Episodes" located to the right of the Baccano! logo. From the episode list that appears on the left, select the last episode labeled "16 - Carol Realizes That the Story Cannot Have an Ending". The quote is located in the episode description in the lower right. including Isaac Dian and Miria Harvent, a pair of eccentric thieves; Firo Prochainezo and his mentor Maiza Avaro, members of Manhattan's small Camorrista Martillo family; Keith, Berga and Luck Gandor, three brothers who manage the small Gandor mafia family, also based in Manhattan; Szilard Quates, who recreates an immortality elixir which many characters accidentally drink, and his homunculus Ennis; Dallas Genoard, a young thug from a wealthy family, and his sister Eve; Czeslaw Meyer, a young boy; mafia hitman Ladd Russo and his fiancée Lua Klein; mute bodyguard Chane Laforet; gangsters Nice Holystone and Jacuzzi Splot; and the Gandors' adoptive brother Claire Stanfield, also known as the legendary assassin Vino.

While developing the series, Narita did not create a detailed outline. Instead, he created the story around on how the characters would act, which changed the original plots and structures of the novels. Although he allows the characters to "move" how they "want", he finds it troublesome because certain characters move "too much" and leave the plot "in ruins"; in addition, other characters are hard to move along with the plot. Tyler Walker, the ADR director of the English dub of the series, states that casting for the series was difficult due to the large number of characters and the character types. The characters Narita created were praised for their differences in appearance and personality, and each was said to have his or her own psychosis.

Creation and conception The author of the light novel series Ryohgo Narita noticed that the large cast in The Rolling Bootlegs seems to have different motives, but intentionally or not, they all move toward the same end. He stated that he never wrote a detailed outline for the book, and so the story was created based on how the characters would act. The characters' actions changed the planned story and structure of the book. During the early drafts, Maiza Avaro was a hypnotist, Ennis was a succubus, and Szilard Quates was able to use magic. In addition, every Camorrista was killed, except for Firo Prochainezo. However, he is happy these ideas were not included in the novels. Narita did not model Firo after anyone, and he believes the character is plain as a result. Although Firo is "supposedly" the protagonist, he found it hard "moving" Firo along with the plot. This problem is solved once Firo's affection for Ennis became apparent. His feelings toward Firo's situation as an Italian immigrant are influenced by an article written by an Italian novelist. The article stated that, as a child, the novelist wished to be like the Italians in the movies because they were happier than the people the novelist saw in real-life.

While planning the two Grand Punk Railroad novels, Narita wanted to create a character that did not act as he looked. So, he placed a large facial tattoo on Jacuzzi Splot, a shy cry-baby. However, Narita never planned for the tattoo to have a meaningful past until he actually wrote the book. As he tried to design Nice Holystone, he wanted an appearance that left a strong impression and designed her with an eyepatch. Upon realizing that many characters sport an eyepatch, Narita decided to have the character wear her eyeglasses over the eyepatch. Other than the source for her appearance, he does not know the inspiration for her obsession with explosives. He also notes that the two novels introduce the series' "number one problem child" Claire Stanfield. He remarks that Claire moves too much by himself (more so than Isaac Dian and Miria Harvent) and changed the entire plot of the novels; for example, all of the Russo and Lemure were supposed to have died. Although Claire is the series' most popular character, Narita will not write a novel featuring him as the protagonist because he believes that the story would end very quickly without any excitement. While writing, Narita did not plan to become attached to Chane, and she was killed in the original draft. However, the author became fond of her, and she survived. Narita comments that Ladd Russo was easier to move around than Claire. He also states that Ladd is his favorite character, and he would often refer back to Ladd's dialogue to raise his spirits.

Casting Tyler Walker, the ADR director of the English dub of the series, comments that because there are a lot of characters and most of them are older men, a character type he does not work with often, choosing voice actors and familiarizing them with their characters was difficult. He asked many directors and actors for recommendations and mainly aimed to cast newcomers, as he felt Baccano! provided him a chance to discover newer talent. Walker wished to find actors who could provide the dialect and accents of the various time periods and locations, especially when casting for the characters with heavy European accents. Walker held auditions for six days, during which about 140 people came for the eighteen main roles. He states that this was probably the longest casting process Funimation has held.

Daily Days The is an information company based in Chinatown that uses its newspaper as a front for information gathering. They gather information by paying visitors, ranging from shopkeepers to mafiosi, and by selling information in exchange for more information. They also employ various people to collect information for them, such as Rachel, who supply the company with information about the incident aboard the Flying Pussyfoot. Many visitors are received at the front desk by Nicholas Wayne or Elean Duga.

President The president is the unseen head of the Daily Days. His office is filled with paper and the sound of ringing phones. His age is unknown due to the large mountain of papers on his desk, but he is described as having a young voice, and was seen by one of his employees who offered him a sugar cube, much to the shock of the two other employees in the office. Important visitors, such as Keith Gandor, are received in his office. He comes off as very wise and polite, often chastising Nicholas when he kept poking fun at fellow employee, Rachel. Although he employs many people to gather information for him, the president seems to know about the situation before they report to him and often knows more than those who witnessed the event. He is voiced by Shō Hayami in the Japanese version and Cole Brown in the English version.

Rachel is an information broker for the Daily Days. Originally, she was the daughter of a railroad engineer that was disgraced after a horrible accident that wasn't his fault. Seeing her father's love for a profession that had rejected him made an impression upon Rachel, and is loath to see anyone hurt as a result of anyone on a train. She had saved Natalie and Mary Beriam during the attack of the Lemures gang during their attack of the Flying Pussyfoot, as well as confronting a blood-covered Claire during his rampage. Although she often rides trains, she does so as a stowaway, never paying her fare. She is voiced by Shizuka Itou in Japanese and Trina Nishimura in English.

Gustav St. Germain and Carol is the vice president of the Daily Days. He and his assistant Carol work primarily on incidents involving the immortals. Gustav seems very interested in stories, and gives Carol "points" for answering rhetorical questions, although Carol is eternally confused by how much these are worth. Carol eventually becomes world-famous during the 2000s. Carol is voiced by Chiwa Saito in Japanese and Kristin Sutton in English.

Nicholas Wayne is the receptionist of the Daily Days. Nicholas originally worked for a military intelligence unit and he taught the employees to use guns, allowing the company to gain enough power to compete with surrounding organizations. Nicholas will sell information to anyone willing to pay the price, regardless of who they are or who else might know the information. His intentions often get the better of him. Because of the nature of their business, thanks to Nicholas the editorial department situated behind the front desk is exceptionally well armed at all times. Nicholas is shown to be very much devious, bribing everyone that comes inside to get his way. Nicholas is voiced by Tohru Furusawa in Japanese and Christopher Bevins in English.

Elean Duga is an employee at the Daily Days. Along with Nicholas, he helps Eve Genoard in her search for Dallas. Unlike Nicholas, Elean is typically eager to help people; however, he also shows a sign of cowardice. Elean is voiced by Taiten Kusunoki in Japanese and by Daniel Drumm in English.

Isaac Dian and Miria Harvent and are a pair of idiotic lovers who work as thieves. Isaac attributes their success to the eccentricity of their good-intentioned crimes, such as stealing watches to steal time or stealing the front door of a museum to prevent anyone from opening the door and entering. They wear a variety of costumes when committing crimes, leading witnesses to assume they are performers. Miria wholeheartedly believes and supports everything Isaac says and often mimics his body language and speech, although she often does not really understand what he is saying. The pair are oblivious to their surroundings, but hold a great affection for the people they meet and believe the best of them. They become immortal in 1930 after mistaking the elixir for a bottle of alcohol. In 1934, Isaac and Miria are confronted by plainclothes officers. Isaac realizes Miria is unaware of this and sends her away without informing her. He is arrested for multiple thefts and imprisoned on Alcatraz Island. Isaac is released later in the year and reunites with Miria in Chicago. They never realized they were immortal until the year 2001. In the English dub of Durarara!!, where the characters make a cameo, Isaac and Miria are played by Sam Riegel and Jennie Kwan respectively.

Gandor family The Gandor family is a small mafia family based in Little Italy, Manhattan. The family is run by three brothers, Keith, Berga and Luck Gandor, who inherited the family from their father and are known for their ruthlessness and fighting ability. Their subordinates are known for becoming violent over slight disagreements. The family refuses to deal in drugs because the brothers possess varying degrees of aversion to them. The family makes money through the illegal distribution of alcohol, underground horse race betting, and various casinos. The family's headquarters is found in the basement of a small jazz hall. Because Luck and the Gandor's adoptive brother Claire Stanfield befriended Firo Prochainezo of the Martillo family as children, the two families are friendly with one another. Other members of the family include Tick Jefferson, Maria Barcelito, and . The Gandor operates on a similar scale as the Martillo family and controls about the same amount of territory.

Gandor brothers , and Luck are brothers who manage the small mafia family in Manhattan. However, the three are described as ill-suited to mafia life. The three become immortal in 1930 after mistaking an immortality elixir for a bottle of alcohol.