Modiano's parents met in occupied Paris during World War II and began their relationship in semi-clandestinity. Modiano's childhood took place in a unique atmosphere: between the absence of his father...of which he heard many troubled stories...and his mother's frequent tours, he had to complete his secondary education by government aid. This brought him closer to his brother, Rudy, who died of a disease at age 10 (the works of Patrick Modiano from 1967 to 1982 are dedicated to him). This disappearance announced the end of the author's childhood, who continued to hold a marked nostalgia for this period.

Modiano studied at the École du Montcel primary school in Jouy-en-Josas, at the Collège Saint-Joseph de Thônes in Haute-Savoie, and then at the Lycée Henri-IV high school in Paris. While he was at Henri-IV, he took geometry lessons from writer Raymond Queneau, who was a friend of Modiano's mother. He received his baccalaureate at Annecy but didn't proceed with his higher education.

His meeting with Queneau, the author of Zazie dans le métro, is crucial. Modiano was introduced to the literary world by Queneau, and this gave him the opportunity to attend a cocktail party given by publishing house Éditions Gallimard. He published his first novel, La Place de l’Étoile, with them in 1968, after having read the manuscript to Raymond Queneau. Starting that year, he did nothing but write.

In 1973, Modiano writes the scenario of Lacombe Lucien, a movie directed by Louis Malle which focuses on the involvement of a boy in the "French Gestapo", after being refused to join the French Resistance. The movie caused controversy due to the lack of justification of the main character's political involvement.

On 12 September 1970 Modiano married Dominique Zerhfuss. "I have a catastrophic souvenir of the day of our marriage. It rained. A real nightmare. Our groomsmen were Queneau, who had mentored Patrick since his adolescence, and Malraux, a friend of my father. They started to argue about Dubuffet, and it was like we were watching a tennis match! That said, it would have been funny to have some photos, but the only person who had a camera forgot to bring the film. There is only one photo remaining of us, from behind and under an umbrella!" (Interview with Elle, 6 October 2003). From their marriage came two girls, Zina (1974) and Marie (1978).