On 11 June 2014, Guingamp announced that they had bought Schwartz from Randers FC. He was their third Danish signing in the summer of 2014, after Lars Jacobsen and Jonas Lössl. He made his debut for the club in the 2014 Trophée des Champions, losing 2–0 to Paris Saint-Germain. On 9 August, he played his first match in Ligue 1, replacing Claudio Beauvue in the 0–2 defeat against Saint-Étienne. On 18 October, he scored his first league goal, in the 1–2 victory away against Lille. He remained in the Guingamp first team for only one season, alternating appearances with the reserve side.