[2] On 20 September 2017, he scored his first professional goal against Radnik Bijeljina, which sent his team through in their cup tie.
[6] He won his first trophy with the club on 22 May, by beating Dinamo Zagreb in the Croatian Cup final.
[15] In September 2024, Lončar moved to Polish club Lech Poznań on a contract until June 2025.
[16] He debuted officially for the team on 14 September in a 5–0 win over Jagiellonia,[17] and provided an assist to Lech's fourth goal.
[18] On 3 February 2025, after being left out of Lech's roster for the winter training camp,[19] Lončar returned to Croatia to join Istra 1961 on a two-and-a-half-year deal.
[22] In January 2018, he received his first senior call-up, for friendly games against the United States and Mexico.