In the 2014 Supercoppa Italiana against Juventus in Doha, Qatar, on 22 December, Koulibaly scored the winning penalty in the shootout to secure Napoli victory. Towards the end of the 2014–15 season, Koulibaly found himself placed in and out of the starting eleven for the side, as manager Rafael Benítez preferred Raúl Albiol and Miguel Britos in the central defence positions. In his first season at Napoli, Koulibaly went on to make 39 appearances and scored one goal in all competitions.