On 6 July 2009, Jallet joined Paris Saint-Germain for a transfer fee of 2.5 million euros, signing a four-year contract. He was recruited to provide competition for Ceará at right-back. Jallet made his first appearance in a competitive match with PSG against Le Mans in the second matchday of the 2009–10 Ligue 1 season. Playing as a right midfielder, he scored his first goal one week later against Valenciennes with an assist from Stéphane Sessègnon. During the next match, against Lille, he delivered an assist a few minutes after he was substituted onto the pitch and marked the very end of game again with a goal. During his first season, Jallet's impact as a substitute with goalscoring potential was highly valued, though gaining a starting berth proved hard with the form of Ceará. Jallet scored again at the 19th match against Grenoble, leading to a 4–0 victory for PSG. He ended the season with 11 assists.