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 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.