Hal is a 17-year-old prodigious intellect and tennis player at the Enfield Tennis Academy. He possesses a vast academic vocabulary and perfect recall, though he struggles with deep feelings of emotional detachment. To cope with the high expectations placed upon him by his family and the academy, Hal secretly smokes marijuana in the school's utility rooms.

Don is a 29-year-old former burglar and current live-in staffer at the Ennet House Drug and Alcohol Recovery House. He has a massive physical build and a history of criminal activity driven by his addiction to narcotics. Now dedicated to his recovery, he cooks meals for the residents and enforces the house rules while relying heavily on the support of local recovery groups.

James is a deceased physicist, avant-garde filmmaker, and the original founder of the Enfield Tennis Academy. He struggled with severe alcohol addiction and clinical depression before dying by suicide in a microwave oven. His artistic outputs include a vast library of commercially unsuccessful films, one of which possesses a dangerously hypnotic power over viewers.

Joelle is a woman from Kentucky who resides at Ennet House to treat her substance addiction. She constantly wears a veil over her face, claiming membership in a support group for disfigured individuals. She previously starred in several experimental films directed by James Incandenza during her relationship with his eldest son.

Hugh is an operative working for the Office of Unspecified Services, a branch of American intelligence. He currently operates undercover disguised as a female journalist named Helen Steeply to track down a highly dangerous film cartridge. His mission involves interviewing people connected to the Incandenza family and negotiating with Quebecois separatists.

Mario is the middle son of the Incandenza family, born with severe physical disabilities and cognitive differences. He walks with the aid of a police lock and acts as the resident filmmaker at the tennis academy. Unlike the other members of his highly intellectual family, Mario is entirely sincere, deeply kind, and immune to cynicism.

Orin is the eldest Incandenza brother, working as a professional football punter for the Arizona Cardinals. After burning out on competitive tennis, he found success in football and relocated to the American southwest. He actively avoids deep conversations about his family trauma, preferring to date a rotating cast of married women he refers to as "Subjects."

Avril is the mother of the Incandenza brothers and serves as the Dean of Academic Affairs at the tennis academy. She maintains a highly composed, almost unnerving exterior and insists on managing the daily lives of the students. Her Canadian background and suspected infidelities are sources of ongoing tension within the family.

Charles is Avril's stepbrother and the current headmaster of the Enfield Tennis Academy. He took over the administrative duties following the death of James Incandenza. He is a highly capable administrator but suffers from intense social awkwardness and physical insecurities.

Michael is an academically gifted student at the tennis academy who runs a lucrative illicit business on campus. He sells drugs and clean urine samples to his fellow athletes to help them beat mandatory drug tests. He is also the acknowledged master of Eschaton, a complex geopolitical wargame played on the tennis courts.

John is the star athlete at the Enfield Tennis Academy. Originally from a mining family in Canada, he plays with mechanical precision and rarely shows emotion. His athletic success is driven by a desire to provide financial stability for his father.

Remy is a member of the Wheelchair Assassins, a militant Quebecois separatist group. He lost his legs in a brutal game of courage during his youth. He secretly communicates with American intelligence in hopes of securing advanced medical treatment for his critically ill wife.

Kate is a young woman suffering from an agonizing, chemical depression that makes basic existence painful. She treats her condition by constantly smoking marijuana, leading to her enrollment in addiction recovery programs. She feels alienated from standard rehab ideology because she does not believe her drug use is her primary problem.

Ken is a professional who struggles with a severe psychological dependence on marijuana. He constructs elaborate, secretive routines around his binges, promising himself each time will be his last. He eventually seeks treatment at Ennet House alongside other recovering addicts.

Gerhardt is the head coach at the Enfield Tennis Academy. He is a strict German disciplinarian who views tennis not just as a sport, but as an existential battle against the self. He designs the punishing physical routines the students endure daily.

Randy is an Ennet House resident with a history of dealing cocaine. While he initially appears to comply with the rehab program, he secretly uses drugs and begins a horrifying routine of capturing and killing stray animals during his nighttime walks to vent his frustrations.

Bruce is a patient at Ennet House who joins the program after a chaotic early adulthood. He frequently accompanies Randy Lenz on evening walks, completely unaware of the dark intentions he disrupts by being present. He carries unresolved trauma from his parents' bizarre deaths.

Pat is the manager of the Ennet House recovery facility. A former wealthy socialite who suffered a stroke due to severe alcoholism, she now uses a wheelchair and dedicates her life to helping others achieve sobriety through tough love.

Fortier is the militant leader of the Quebecois separatist group known as the Wheelchair Assassins. He relentlessly searches for the master copy of the Entertainment, intending to use it as a weapon against the United States to force Canadian independence.

Poor Tony is a street-level criminal and heroin user navigating the worst throes of withdrawal. Wanted by dangerous individuals for a past mistake involving poisoned drugs, he resorts to stealing purses to survive, eventually sparking a violent street chase.

Matty is Michael Pemulis's older brother. Unlike Michael, who found a place at an elite academy, Matty works as a sex worker and grapples with severe trauma stemming from an abusive father. He maintains ties to the criminal underbelly of Boston.