Weah was named to the first-team squad for a Ligue 1 fixture against Troyes AC on March 3, 2018, while the club's starting forwards were rested for an upcoming Champions League match. He came on as a substitute in the 79th minute of the match and had a goal-scoring opportunity in stoppage time that was saved by the Troyes goalkeeper. Weah made his first start for Paris Saint-Germain in a 0–0 draw against SM Caen on the last day of the Ligue 1 season. Weah scored his first competitive goal for PSG during a 4–0 win against Monaco in the Trophée des Champions on August 4, 2018. He scored his first league goal a week later in the club's season opener, a 3–0 win over Caen.