On 4 June 2018, Kovačić was selected in Zlatko Dalić's 23-man squad for the 2018 FIFA World Cup. On 22 June, Kovačić provided an assist to his teammate Ivan Rakitić as he scored Croatia's third goal in a 3–0 win over Argentina in their second group stage match of the tournament. Croatia was beaten 4–2 by France in the final on 15 July.