2009-10: Fredric Larsson played 15 games for the Brynas U18 and U16 teams and skated for Gastrikland in the TV-Pucken tournament for high school-aged players. He had 1 assist with 8 penalty minutes in his limited action with the Brynas squads and in eight games for Gastrikland had 2 assists and 6 penalty minutes.
2010-11: Larsson played in 41 games including five playoff contests in his first full season with the Brynas U18 team. In 36 regular season games he scored 6 goals with 18 assists and was plus-48 with a team-leading 73 penalty minutes. Brynas finished first in Allsvenskan U18 North and reached the semifinals in the playoffs. In five playoff games Larsson was plus-one with no points and 6 penalty minutes.
2011-12: Larsson appeared in 16 SuperElit league games with Brynas U20 and led the Brynas U18 team in penalty minutes for the second season in a row. In 14 regular season games for the third-place Brynas U20 team he scored 1 goal with 3 assists and was plus-two with 24 penalty minutes. In the two-game playoff series with Sodertalje he was minus-one with 6 penalty minutes. Larsson racked up 158 penalty minutes in 35 game with the Brynas U18 team but was plus-33 with 3 goals and 12 assists. Brynas finished fourth and reached the U18 playoff semifinals. In five playoff games Larsson scored 1 goal and was plus-one with 8 penalty minutes. Not among the 120 European skaters in Central Scouting's final rankings prior to the 2012 NHL Draft he was selected by Philadelphia in the fourth round (111th overall).
2012-13: Larson played 41 games for Brynas in Sweden's SuperElit U20 league and led the league with 134 penalty minutes. He was +1 and scored 4 goals with 6 assists. Brynas finished ninth in the SuperElit league Top 10. Larsson did not play in the two playoff games against MODO.
Larsson has moved over to the USHL for 2013-14 to play for the Youngstown Phantoms.