[12] On 18 December, he was in a matchday squad for the first time, sitting on the bench for Nicolas Douchez in a 2–1 win over Saint-Étienne in the last 16 of the Coupe de la Ligue.

[13] On 19 January 2014 he was included in a Ligue 1 game for the first time, remaining unused as Salvatore Sirigu played in a 5–0 win over Nantes at the Parc des Princes.

[15] He made his professional debut on 18 September in a 1–1 draw at Rennes, as a substitute for Yassine Benzia after Vincent Enyeama was sent off in the 69th minute.

In the second game of the season, a 3–0 loss at Strasbourg, he was sent off for throwing the ball at an opponent and striker Nicolas de Préville had to go in goal for the final minutes.

[17] The following season, he was an ever-present as Lille finished as runners-up to PSG, and was elected Goalkeeper of the year in the Trophées UNFP du football.

[32] On 18 April 2023, he saved a penalty from Khvicha Kvaratskhelia during a 1–1 away draw against Napoli in the 2022–23 UEFA Champions League quarter-final second leg, which helped his team to qualify to the semi-final, by winning 2–1 on aggregate, for the first time since the 2006–07 season.

[41] He made his debut on 7 October 2020 as a half-time substitute for Steve Mandanda in a friendly against Ukraine, which ended as a 7–1 win at the Stade de France.

[43] On 6 June 2022, Maignan made his competitive international debut in a 1–1 UEFA Nations League draw away to Croatia, conceding a late penalty by Andrej Kramarić.

[45] Following Hugo Lloris's retirement from international football in January 2023, Maignan was promoted to first choice goalkeeper for the France national team.