2010-11: Anton Karlsson appeared in four games with the Frolunda U18 team as a 14-year-old and played for Goteborg 2 in the annual TV-Pucken tournament for Swedish high school age players. He had 1 assist with the Frolunda U18 team. Karlsson scored 7 goals with 1 assist in eight TV-Pucken games.
2011-12: Karlsson spent most of the year with Frolunda’s U18 team and played for Sweden’s U16 and U17 teams in international play as well as skating for Goteborg in the TV-Pucken tournament. Karlsson scored 12 goals with 19 assists in 28 U18 games and was +20 with 32 penalty minutes. Frolunda won the U18 bronze medal. In three matches with Sweden’s U17 team Karlsson scored 2 goals with 1 assist and he scored 2 goals with 6 assists in eight games with Sweden’s U16 team. He scored 6 goals with 6 assists in eight TV-Pucken games.
2012-13: Karlsson played for Sweden’s U18 team in the 2013 Ivan Hlinka Memorial Tournament in August before returning to Frolunda — where he split the season between the U20 and U18 squads. He later represented Sweden in the 2013 U17 World Hockey Challenge, where he was the team captain, and at the 2013 U18 World Junior Championship. He played 20 games in Sweden’s SuperElit U20 league, including three playoff games, and scored 5 goals with 5 assists; finishing +7 with 4 penalty minutes. In 23 games for Frolunda’s U18 team he scored 20 goals with 19 assists and was +12 with 64 penalty minutes. In three U18 playoff games he scored 1 goal with 3 assists and was +2. Karlsson had 2 assists and was +3 in five games at the Ivan Hlinka Tournament and was an assistant captain for the U18 team at the WJC. He scored 2 goals with 2 assists and was +3 with 10 penalty minutes in five games at that tournament. Sweden’s U17 team won the gold medal at the WHC and Karlsson scored 6 goals with 3 assists and 22 penalty minutes in six games.
2013-14: Karlsson skated in his second straight Ivan Hlinka Tournament in August — serving as a team captain for Sweden’s seventh-place squad before returning to Frolunda’s U20 team. In four games at the Ivan Hlinka Tournament he scored 1 goal with 4 assists.
Karlsson is a quick, north-south winger who likes to play an aggressive game. Possesses good size and a husky build, which he likes to incorporate in his game with every opportunity. A bit of a truck when he’s at full speed and has been too much for opponents physically at Sweden’s junior levels. Karlsson comes to work with the lunch pail in his hand and then goes to battle. Like Kempe, he too likes to finish his checks and make life difficult for opponents in corners. Has shown the ability to be a finisher or a playmaker, often flashing a surprisingly good eye for finding his teammates. Looks to have a promising pro career in light of how ready he is to do whatever the team needs and the coaches ask of him. A player for any role that is needed. He’s got a solid skill set, although everything will need to continue improving in the years to come, shot variations included. Karlsson is very confident, and is looking forward to taking a much bigger step next winter and would seem an absolute lock for his nation’s WJC squad.
Karlsson's physical style has led to injuries and there will naturally be questions about durability heading forward, despite a good frame and strong build. His overall offensive upside is questionable at best as he’s only been a real impact scorer at the U18 level domestically, having just had a winter in which he generated little offensively in his international appearances. Having been outstanding and very promising in the 12-13 season, his 13-14 season – although hampered by the aforementioned injuries – wasn’t one in which he was able to improve upon his previous development.