Henry Hill, Jimmy Conway and Tommy DeVito are in a car late at night; Henry is driving while the other two men sleep. When they pull over to check where the noise is coming from, they find that the dead body that they have been hiding in the trunk is actually alive and banging to get out. Henry opens the trunk and Tommy stabs the man violently before repeatedly shooting it to ensure it's dead. Henry narrates, "As far back as I can remember, I always wanted to be a gangster."
From here, we go back in time to the 1950s and see the young Henry Hill idolizing and then slowly becoming involved in the Lucchese family gang who run his predominantly Italian, blue-collar neighborhood in East Brooklyn, New York. He quits school in 1955 and becomes the protégée of Lucchese boss Paulie Cicero and his wingman Jimmy Conway. Henry is partnered with fellow youngster Tommy DeVito, and they sell bootleg cigarettes that Jimmy gives them. During one such transaction, they are busted by detectives who arrest Henry. When Henry goes to court and keeps silent, he is celebrated by the gangsters and welcomed into the Lucchese family.
The Henry/Tommy partnership endures into adulthood, and both men become more and more entrenched in the gangster lifestyle. Along the way, Henry meets Karen Hill, a Jewish girl, and the pair fall in love and get married as Karen slowly gets seduced into the life of a mob wife. They start a family as Henry continues to climb the ranks in the mafia. Tommy and Henry conspire with Jimmy to steal millions of dollars worth of cargo from Kennedy International Airport, making a lot of money for the family, which earns Henry a great deal of trust with Paulie. Over the next few years their activities become more dangerous and reckless. Jimmy is a wild man in his own right, and Tommy demonstrates a violent, psychotic streak by needlessly killing a young waiter named Spider.
By 1970, Tommy's temper and sadistic streak has only gotten worse, as he brutally murders a made man from the rival Gambino family, a man named Billy Batts, just because he teased Tommy a little. Because the murder could likely start a war with the Gambino family, Jimmy, Tommy and Henry take the body to an abandoned field to bury Batts, which explains the first scene in the movie.
When Henry starts to cheat on Karen and she discovers he has a mistress, their marriage begins to unravel. Paulie convinces Karen to stand by Henry, assuring her that he will return to her in time, and sends Henry with Jimmy to Florida to call in a debt owed to Paulie. Jimmy and Henry find the man who owes the money and dangle him over the lion cage at a zoo in Tampa. However, the man's sister works for the F.B.I. and both Henry and Jimmy end up jailed for four years as a result of the incident. In prison, Henry develops a thriving drug business which he wants to pursue when he is released, but Paulie is against this, as there are particularly punitive sentences for bosses whose men are running drugs. Henry ignores the warning and involves not only Jimmy and Tommy in the operation but also Karen and his new mistress Sandy. In the midst of this, Jimmy plans and successfully executes the biggest heist to date at Lufthansa's cargo terminal, bringing in $6 million. After the heist, Jimmy becomes increasingly paranoid as his co-conspirators start to flaunt their new money. In order to keep his peace of mind, he begins having each of the men murdered. At the same time, the trio learn that Paulie is going to turn Tommy into a made man. On the day of his ceremony, however, the Lucchese elders kill Tommy because of the Batts murder and his reckless behavior.
The film shifts to a momentous day in Henry's life: Sunday, 11th May, 1980. All the messy threads of Henry's life all collide. Henry has a large cocaine shipment that needs to get out, a family meal to make and host, a mistress to calm down, all while high on cocaine, and being followed by a surveillance helicopter. Backing out of the driveway at the end of the night, Henry is arrested and brought in for questioning. Karen bails Henry out of jail, but in the activity of the arrest, flushes all of his remaining cocaine down the toilet, leaving them penniless. Paulie and the family abandon Henry after his drug arrest. Karen goes to Jimmy to let him know that Henry is sober again and his silence is guaranteed, but Jimmy makes it clear to Karen that any loose talk will cost them both their lives. When it becomes clear that Henry's life is endangered, he turns himself in to become an F.B.I. informant. He and his family enter the Federal Witness Protection Program and live with changed names in total anonymity. He accepts his banal existence in the suburbs, but still dreams of the life of a gangster.
