Plot

A boy growing up on Long Island seeks out father figures among the patrons at his uncle's bar.

A boy (Jr.) seeks a replacement for his father, who disappeared shortly after his birth, and bonds with his uncle Charlie and the patrons at a bar in Long Island. Uncle Charlie works as a bartender there and knows all of the staff and regular patrons. He is a charismatic individual and all of his friends are eager to initiate Jr. into their rituals. Jr. listens closely to the stories of these men and relies on these stories for guidance on how to live.—Frank Liesenborgs

In 1973, nine-year-old JR Maguire (Daniel Ranieri) and his mother Dorothy (Lily Rabe) move back in with her parents on Long Island. Dorothy had failed to pay rent for the last 5 months and had no choice. Dorothy wanted to escape Long Island and considered herself a failure for having to come back. But JR loved it. Abandoned by his deadbeat father Johnny (Max Martini), a radio DJ known as "the Voice", JR grows up with his mother's working-class family. He finds a surrogate father in his uncle Charlie (Ben Affleck), the owner of a local bar, "The Dickens". Charlie tells JR that he is not good at sports. JR says that he likes to read. Charlie asks JR not to depend on his father too much.

JR often listens to the Voice on the radio, and Johnny calls with plans to take him to a baseball game but fails to show up and later flees the state as he was being arrested for non-payment of child support. Imparting life lessons to JR, Charlie shares his love of reading and encourages him to become a writer, while Dorothy is determined that her son will have the college education she never had. JR considers Charlie to be his role model and has his heart set on being a writer. Though Dorothy's own well-educated father never made anything of his life, she insists that JR will one day attend Harvard or Yale and become a lawyer.

Johnny makes a brief visit, beating up Charlie when he heckles him for his absence in JR's life. Confronting a school psychologist for exploiting JR to hit on Dorothy, Charlie is impressed by his nephew's writing. Charlie knows JR can be a good writer and moves him to reading more advanced books to widen his horizons. School organizes a father son breakfast event and JR is depressed since his father is not there to be with him. JR's grandfather (Christopher Lloyd) accompanies him to a father-and-son breakfast and explains that Dorothy is having her cancerous thyroid removed. She recovers, and JR's knack for word puzzles earns him a spot in Charlie and his friends' bowling league. Charlie's friends Bobo (Michael Braun), Chief (Max Casella) & Joey D (Matthew Delamater) love JR as he is a prodigy at solving the word puzzles.

As a teenager, JR (Tye Sheridan) has an interview at Yale and meets a priest on the train to New Haven. He is admitted to the university with full scholarship, to his family's delight, and later brings his roommates home to meet Charlie, having their first of-age drinks at The Dickens. Roommates are Jimmy (Ivan Leung) & Wesley (Rhenzy Feliz). JR strikes up a romance with his classmate Sidney (Briana Middleton), who brings him home to Westport, Connecticut. After sneaking him up to her room for the night and having sex with him, leading to an uncomfortable breakfast with her "lower-upper-middle class" parents before he departs. Lower-Upper-Middle class are people who think they are rich but are really not. Sidney's mother insults JR by saying that his mother is optimistic that JR will study to become a lawyer.

JR spends the next 2 years trying to excel at his studies. Continuing his studies, JR encounters the same priest on the train on his way back home and is unsuccessful in winning Sidney back. Sidney tells JR that she is seeing someone else. JR starts to write his first novel and working at the bar to earn some extra cash. He has decided at this point that he is not going to be a lawyer. Graduating in 1986, he receives one of his father's sporadic phone calls. JR presents his mother with a class ring but disappoints her by eschewing law school and moving home to work on his novel. Ignoring his friend Wesley's (Rhenzy Feliz) advice, he continues to pursue Sidney with guidance from Charlie, and is hired as a trainee at The New York Times. Sidney and his mother tell JR that publishing is going toward memoirs these days.

JR has trouble with his editor at the paper, and the editor wants JR to do things as they are done at The Times. Like using the Dot after initials. He is not open to new ideas from JR. Learning that Sidney has married her college boyfriend, JR gets drunk and is eventually let go from the Times. The editor says that JR's writing was good, but for some undisclosed reason, he was not offered a full-time position as a reporter. He is advised to work at smaller newspapers to build his experience. Charlie is briefly hospitalized and encourages JR to incorporate his recent setbacks into his novel. On Charlie's advice, JR finds his father in North Carolina, but realizes that he remains an abusive alcoholic. Johnny assaults his girlfriend and JR has him arrested, finally standing up to his father.

Returning home, where his mother has found a new job, JR moves to Manhattan, but not before Charlie gives him his car. Charlie and his drinking buddies see his nephew off, and JR is determined to prove himself as a writer. During the credits, young JR spends a day at the beach with Charlie and his friends.