In 1977, high school dropout Eddie Adams (Mark Wahlberg) struggles to find his place in the world while living with his emotionally abusive mother and father in Torrance, California. Working at a nightclub managed by Maurice Rodriguez, he encounters porn filmmaker Jack Horner (Burt Reynolds). Jack sees potential in Eddie and auditions him by observing a sexual encounter with the skater porn star Rollergirl (Heather Graham), leading Eddie to dive headfirst into the adult film industry.
After a heated confrontation with his disgruntled mother about his love life, which she derides as shameful, Eddie moves in with Jack in San Fernando Valley. He adopts the stage name Dirk Diggler and quickly rises to fame due to his striking looks, youthful charm, and uniquely impressive endowment. As his star shines brightly, Dirk enjoys the fruits of his labor, upgrading his lifestyle with a lavish home, an extensive wardrobe, and a classic “competition orange” 1977 Chevrolet Corvette. Together with fellow adult film star Reed Rothchild (John C. Reilly), Dirk pitches a series of dynamic, action-packed porn films to Jack and financier Col James. These ventures prove to be massive successes, providing a glimpse into the carefree and hedonistic lifestyle typical of the late 1970s disco era.
As New Year’s Eve 1980 approaches, however, chaos erupts at one of Jack's parties when assistant director Little Bill Thompson (William H. Macy) discovers his wife cheating, resulting in a tragic murder-suicide. Consumed by the allure of drugs, Dirk and Reed indulge in cocaine as their careers flourish. Despite accumulating numerous awards from the Adult Film Association, Dirk’s drug use leads to impotence and volatile mood swings, causing friction with Jack, especially as new competitors like Johnny Doe enter the scene.
By 1983, the tension escalates after a heated argument with Jack about shooting a scene while Dirk is high. Feeling rejected, Dirk decides to embark on a music career with Reed and Scotty (Philip Seymour Hoffman), another close companion fascinated by Dirk. Yet, the trio struggles to secure a recording contract, confronted by financial barriers.
Simultaneously, Jack faces his own set of challenges as he debuts a variety of projects while grappling with the pressures applied by theater magnate Floyd Gondolli (Philip Baker Hall) to switch his films to videotape. His disillusionment grows, especially when involved in a disturbing scene with Rollergirl, leading them to confront a man who recognizes her from their past.
In September 1983, fellow star Amber Waves (Julianne Moore) finds herself embroiled in a custody battle that threatens her relationship with her child due to her career choices and substance abuse issues. Meanwhile, Buck Swope (Don Cheadle) strives to establish a stereo equipment store but is thwarted by his criminal past.
As desperation mounts, Dirk and Reed are unable to finance their demos and resort to dangerous decisions, leading them to a confrontation with local drug dealer Rahad Jackson (Alfred Molina). In a chaotic exchange, their friend Todd Parker (Thomas Jane) tragically loses his life, while Dirk reconciles with Jack amid the fallout.
Moving into 1984, the characters confront the repercussions of their past. Buck and Jessie welcome a son, and various side stories unfold as they all strive to piece their lives back together. Despite the turmoil, Dirk and Amber are poised to reclaim their footing in the industry, aiming to re-enter the world of filmmaking.
