After spending the first half of the season on the bench, having played more minutes for the national team than the club, Rebić scored his first two league goals in a 3–2 victory over Udinese on 19 January 2020, having come on as a half-time substitute for Giacomo Bonaventura. A week later, he continued his super sub goalscoring run with a single goal in a 1–0 away victory over Brescia. On 9 February, he scored the opener in "Derby della Madonnina"; however, the game ended as a 4–2 victory for Inter Milan. Four days later, he scored Milan's only goal in a 1–1 draw with Juventus in Coppa Italia. On 17 February he scored the only goal in a 1–0 victory over Torino. On 12 June, in the club's first game after the COVID-19 pandemic, the second leg of Coppa Italia fixture against Juventus, Rebić was sent off after sixteen minutes due to a rough tackle on Juventus' defender Danilo. On 4 July, he scored the third goal in a 3–0 victory over title contenders Lazio, their first home defeat of the season. On 7 July, he won a penalty, provided an assist and scored in a 4–2 comeback victory over Juventus.