Sam Spade: Sam Spade is the hero of the novel. He is a detective, who worked for a large agency before branching out on his own in San Francisco. He has a very defiant attitude towards law, which he portrays to the maximum to clients, able to maintain his defiance in a way that doesn't compromise his practice.
Sam Spade has a very cynical and one might say a very 'typical' attitude towards women according to the time this novel was set in. Women were gaining independence in the early 1920s and 30s, and Sam Spade would probably remember the time women were not allowed to vote in the United States. He seemed to be in love with Brigid O' Shanughnessy's character, and yet he hands her over to the ploce for committing the murder of his partner Miles. Sam Spade's character didn't make any sense to me at first. The driving force behind Sam Spade is a complex morality which sometimes sits at odds with his character portrayal by the author. But the writer probably wanted the readers to feel empathy towards Sam Spade's character, but in the modern times, his attitude towards women would earn him a black eye for sure.
Casper Gutman: is an enterprising and opportunistic criminal who wants the "Maltese Falcon" statue and has been chasing it all over the globe for seventeen years. He is successful in presenting a jovial front, even in high level criminal dealings and anger. He has been very intricately, crafted by the writer, because even though he is a thief, he is not a very negative or evil character as criminals would be expected to be. He has a generally jolly and personable even when he fails to occupy the much coveted Maltese Falcon. As a character he seemed more likeable than Sam Spade.
Brigid O'Shaughnessy: originally is the person who hires Spade and Archer with an false story about trying to find a man who ran off with her younger sister. She also uses an alias: Ms. Wonderly. Her major objective in doing this was to have her partner in crime, Floyd Thursby followed. This is a deceitful character in its most obvious and classical description. The characterization is somewhat a stereo type of a female villain, who seems to have no morals and seems to have no conscious. She is the murderer of Miles Archer. She is manipulative and plays games with most characters. She even fools some that she is a nice person, but impatience shapes her downfall. In reality she possess' a treacherous heart and only cares about her own self interest.
Wilmer Cook: used to work as Gutman's secretary, Wilmer is a young man who tries to main a tough and intimidating façade which is shattered without many problems by Sam Spade. He has a quick temper and takes his hate of Sam Spade out on other people. He has no problems drawing his guns to kill someone. He lacks patience and thinks too highly of himself. Unfortunately for him, Sam quite easily disarms him several times. This shows that he is not the kind of person who would learn from his mistakes. It seems that Wilmer and Cairo must at one time share a close relationship, but Wilmer shows no respect for him, and verbally abuses him every chance he gets.
Joel Cairo: Joel Cairo is sometimes referred to as "the Levantine" which probably indicates the eastern Mediterranean area he appears to belong to. He is very effeminate in the way he talks and dresses. He likes to come across as a 'man of the world." He has originally hired Sam Spade to find the elusive Maltese Falcon, after he has Spade's offices ransacked at gunpoint. He is also not strong enough to fight for himself, especially when he is punched by Sam Spade and when he gets into a fight with Brigid. He also has zero scruples. He helps to drug Sam who then gets beaten up by Wilmer Cook. He is mostly motivated by greed.
Effie Perrine: is Sam Spade's secretary and confidante, in the Maltese Falcon. This seems to be the only character who does not have any ulterior motives or unscrupulous machinations. She also seems to have a crush on her boss. She seems to hold Sam together and she takes care of him. She doesn't question him, even when he calls her in the middle of the night. She comes across as an intelligent character, who fulfills the need of the hour.
Iva Archer: is Miles Archer's wife in novel. She and Sam Spade shared a close relationship at one time, but it seems that Sam Spade hates her. This is evident when he goes to great lengths to avoid her after Miles Archer has been murdered. Seeing him with Brigid O'Shaunghnessy, Iva become jealous and acts in a very vindictive manner.
Miles Archer: is Sam Spade's partner in their detective agency. Miles seems to be very taken with Brigid O'Shaughnessy's good looks and offers to handle her case personally. He dies, because he is concentrating more on Brigid, than on the job at hand, and also behaving inappropriately with a client. He gets shot by the same client. Sam Spade, it seems hated Miles Archer and was going to throw him out of the business soon.
Phil Archer: is Miles Archer's brother in the novel. Even though he doesn't appear in the novel, he is basically the one that suspects Sam Spade killed Miles Archer and tells this story to the police.
Ted Christy: Christy is Effie's cousin, a professor of history at the University of California at Berkely. Effie is sent to Christy by Spade in order to get a better idea about the worth and authencity of the "Maltese Falcon" and the story surrounding it.
Lieutenant Dundy: a policeman who is repeatedly comes to visit Spade to find out about what he knows about the events related to Miles Archer's death. Dundy is a hardened police officer, who suspects Spade as the murderer of his partner. He comes across as very jealous of Sam Spade and is hatching up schemes to at least try to get Sam Spade's detective license revoked.
Mr. Filcraft: a character belonging to Sam Spade's past. In my opinion, not very instrumental in the original plot of the novel.
Mr. Freed: works at a St. Mark's Hotel desk, where Brigid is registered as Ms. Wonderly as the story begins. He is a discreet gentleman and proves very instrumental to Spade by providing valuable information to him.
Rhea Gutman: Mr. Gutman's daughter, appears only once in the novel. Sam Spade finds the seventeen year old drugged after he goes to the Alexandria Hotel to try to look for Brigid O'Shaunghnessy. Spade later finds out that after sending him on a wild goose chase she exits the hotel without any traces of being drugged at all. Her roll in the drama, other than misleading Sam for awhile, was not very important.
Captain Jacobi: The captain and carrier of the Maltese Falcon for Brigid O'Shaunghnessy from Hong Kong. He delivers the statue to Sam Spade's office, where he dies as he has been shot several times. Its not clear how he got to Sam's office despite being shot, and still managing to retain the Maltese Falcon to hand over to Sam Spade.
Luke: Luke works as a house detective at the Hotel Belvedere, where Joel Cairo was staying. It is not clear why, but he keeps Spade informed about Cairo's activities. He also chases Wilmer out of the hotel on Spade's goading.
Floyd Thursby: also never appears in the novel physically. He is a crook from St. Louis and Chicago, who met Brigid O' Shaunghnessy in Hong Kong and helped her steal the Maltese Falcon. Brigid hires Spade and Archer to follow Thursby, in the hope that he would either be killed or scared away. Wilmer killed Thursby to try to scare Brigid into revealing the whereabouts of the statue.
Sid Wise: is Sam Spade's lawyer and is a member of the firm Wise, Merican and Wise. He is consulted too many times by Sam Spade to make sure the strategies he is plotting are legal or not. Spade sends Iva Archer to Wide after she has given the police information, saying that Wise will protect her legally.