A helicopter transports a statue of Christ over an ancient Roman aqueduct outside Rome while a second, Marcello Rubini’s news helicopter, follows it into the city. The news helicopter is momentarily sidetracked by a group of bikini-clad women sunbathing on the rooftop of a high-rise apartment building. Hovering above, Marcello uses gestures to elicit phone numbers from them but fails in his attempt then shrugs and continues on following the statue into Saint Peter’s Square.
Marcello meets Maddalena by chance in an exclusive nightclub. A beautiful and wealthy heiress, Maddalena is tired of Rome and constantly in search of new sensations while Marcello finds Rome suits him as a jungle he can hide in. They make love in the bedroom of a prostitute to whom they had given a ride home in Maddalena’s Cadillac.
Marcello returns to his apartment at dawn to find that his fiancée, Emma, has overdosed. On the way to the hospital, he declares his everlasting love to her and again as she lies in a semiconscious state in the emergency room. While waiting frantically for her recovery, however, he tries to make a phone call to Maddalena
That day, he goes on assignment for the arrival of Sylvia, a famous Swedish-American actress, at Ciampino airport where she is met by a horde of news reporters.
During Sylvia’s press conference, Marcello calls home to ensure Emma has taken her medication while reassuring her that he is not alone with Sylvia. After the film star confidently replies to the barrage of journalists’ questions, her boyfriend Robert (Lex Barker) enters the room late and drunk. To Sylvia’s producer, Marcello casually recommends that Sylvia be taken on a tour of St Peter’s.
Inside St Peter’s dome, a news reporter complains that Sylvia is “an elevator” because none of them can match her energetic climb up the numerous flights of stairs. Inspired, Marcello maneuvers forward to be alone with her when they finally reach the balcony overlooking St. Peter’s Square.
That evening, the infatuated Marcello dances with Sylvia in the Baths of Caracalla. Sylvia’s natural sensuality triggers raucous partying while Robert, her bored fiancé, draws caricatures and reads a newspaper. His humiliating remark to her causes Sylvia to leave the group, eagerly followed by Marcello and his paparazzi colleagues. Finding themselves alone, Marcello and Sylvia spend the rest of the evening in the alleys of Rome where they wade into the Trevi Fountain.
Like a magic spell that has suddenly been broken, dawn arrives at the very moment Sylvia playfully “anoints” Marcello’s head with fountain water. They drive back to Sylvia’s hotel to find an enraged Robert waiting for her in his car. Robert slaps Sylvia, orders her to go to bed, and then assaults Marcello who takes it in stride.
Marcello meets Steiner, his distinguished intellectual friend, inside a church playing Bach on the organ. Steiner shows off his book of Sanskrit grammar. The two continue playing the piano, even offering up some jazz pieces for the watching priest.
Late afternoon, Marcello, his photographer friend Paparazzo, and Emma drive to the outskirts of Rome to cover the story of the purported sighting of the Madonna by two children. Although the Catholic Church is officially skeptical, a huge crowd of devotees and reporters gathers at the site.
That night, the event is broadcast over Italian radio and television. Blindly following the two children from corner to corner in a downpour, the crowd tears a small tree apart for its branches and leaves said to have sheltered the Madonna. Meanwhile, Emma prays to the Virgin Mary to be given sole possession of Marcello’s heart.
The gathering ends at dawn with the crowd mourning a sick child, a pilgrim brought by his mother to be healed, but trampled to death in the melee.
One evening, Marcello and Emma attend a gathering at Steiner’s luxurious home where they are introduced to a group of intellectuals who recite poetry, strum the guitar, offer philosophical ideas, and listen to sounds of nature recorded on tape. An American woman, whose poetry Marcello has read and admired, recommends that Marcello avoid the “prisons” of commitment: “Stay free, available, like me. Never get married. Never choose. Even in love, it’s better to be chosen.” Emma appears enchanted with Steiner’s home and children, telling Marcello that one day he will have a home like Steiner’s, but he turns away moodily.
Outside on the terrace, Marcello confesses to Steiner his admiration for all he stands for, but Steiner admits he is torn between the security that a materialistic life affords and his longing for a more spiritual albeit insecure way of life. Steiner philosophizes about the need for love in the world and fears what his children may grow up to face one day.
Marcello spends the afternoon working on his novel at a seaside restaurant where he meets Paola, a young waitress from Perugia playing Perez Prado’s cha-cha “Patricia” on the jukebox and then humming its tune. He asks her if she has a boyfriend, then describes her as an angel in Umbrian paintings.
Marcello meets his father (Annibale Ninchi) visiting Rome on the Via Veneto. With Paparazzo, they go to the Cha-Cha-Cha Club where Marcello introduces his father to Fanny, a beautiful dancer and one of his past girlfriends (he had promised to get her picture in the paper, but failed to do it). Fanny takes a liking to his father. Marcello tells Paparazzo that as a child he had never seen much of his father, who would spend weeks away from home. Fanny invites Marcello’s father back to her flat, and two other dancers invite the two younger men to go with them. Marcello leaves the others when they get to the dancers’ neighborhood. Fanny comes out of her house, upset that Marcello’s father has become ill.
Marcello’s father has suffered what seems to be a mild heart attack. Marcello wants him to stay with him in Rome so they can get to know each other, but his father, weakened, wants to go home and gets in a taxi to catch the first train home. He leaves Marcello forlorn, on the street, watching the taxi leave.
Marcello, Nico, and other friends met on the Via Veneto are driven to a castle owned by aristocrats at Bassano di Sutri outside Rome. There is already a party long in progress, and the party-goers are bleary-eyed and intoxicated. By chance, Marcello meets Maddalena again. The two of them explore a suite of ruins annexed to the castle. Maddalena seats Marcello in a vast room and then closets herself in another room connected by an echo chamber. As a disembodied voice, Maddalena asks him to marry her; Marcello professes his love for her, avoiding answering her proposal. Another man kisses and embraces Maddalena, who loses interest in Marcello. He rejoins the group, and eventually spends the night with Jane, an American artist and heiress.
Burnt out and bleary-eyed, the group returns at dawn to the main section of the castle, to be met by the matriarch of the castle, who is on her way to mass, accompanied by priests in a procession.
Marcello and Emma are alone in his sports car on an isolated road. Emma starts an argument by professing her love, and tries to get out of the car; Marcello pleads with her not to get out. Emma says that Marcello will never find another woman who loves him the way she does. Marcello becomes enraged, telling her that he cannot live with her smothering, maternal love. He now wants her to get out of the car, but she refuses. With some violence (a bite from her and a slap from him), he throws her out of the car and drives off, leaving her alone on a deserted road at night. Hours later, Emma hears his car approaching as she picks flowers by the roadside. She gets into the car with neither of them saying a word.
Marcello and Emma are asleep in bed, tenderly intertwined; Marcello receives a phone call. He rushes to the Steiners’ apartment and learns that Steiner has killed his two children and himself.
After waiting with the police for Steiner’s wife to return home, he meets her outside to break the terrible news while paparazzi swarm around her snapping pictures.
An unspecified amount of time later, an older Marcello—now with gray in his hair—and a group of partygoers break into a Fregene beach house owned by Riccardo, a friend of Marcello’s. Many of the men are homosexual. To celebrate her recent divorce from Riccardo, Nadia performs a striptease to Perez Prado’s cha-cha “Patricia”. The drunken Marcello attempts to provoke the other partygoers into an orgy. However, their inebriation causes the party to descend into mayhem with Marcello throwing pillow feathers around the room as he rides a young woman crawling on her hands and knees. Riccardo shows up at the house and angrily tells the partiers to leave.
The party proceeds to the beach at dawn where they find a modern-day leviathan, a bloated, stingray-like creature, caught in the fishermen’s nets. In his stupor, Marcello comments on how its eyes stare even in death.
Paola, the adolescent waitress from the seaside restaurant in Fregene, calls to Marcello from across an estuary but the words they exchange are lost on the wind, drowned out by the crash of the waves. He signals his inability to understand what she is saying or interpret her gestures. He shrugs and returns to the partygoers; one of the women joins him and they hold hands as they walk away from the beach. In a long final close-up, Paola waves to Marcello then stands watching him with an enigmatic smile.