Partey made his first team debut for Atlético Madrid on 28 November 2015, replacing Luciano Vietto in a 1–0 home win against Espanyol. On 2 January of the following year, he scored his first league goal for the club, netting the game's only strike in a home success over Levante. On 28 May, he played in the UEFA Champions League Final against Real Madrid, replacing Koke in the 116th minute as his side lost on penalties.