A native of Karlstad, Sweden, Carlsson has represented his country at numerous international tournaments, including the 2023 World Championship (2-3=5 points with a +5 rating in eight games) where he was the youngest-ever player to score a goal for Sweden on May 14 vs. Austria (18 years, 138 days) and the youngest Swede to appear at the tournament May 12 vs. Germany (18 years, 136 days). Carlsson scored 3-3=6 points with a +4 rating for Sweden at the 2023 World Junior Championship, ranking third among Sweden skaters in points and goals as one of two underage forwards. He helped Sweden to a gold medal at the 2022 U-18 World Championship (scored 2-1=3 points in two games) and also earned bronze for his country at the 2021 Hlinka Gretzky Cup.