2008-09: Joel Vermin split time between Bern's U-18 and U-20 squads. In 28 U-18 games, Vermin scored 29 goals and added 25 assists for 54 points. In 8 playoff games for this squad, Vermin scored 7 goals and added 9 assists for 16 points. In 13 games at the U-20 level, Vermin scored 3 goals and added 5 assists for 8 points.
2009-10: Vermin made his debut in the Swiss National A league as a 17-year-old, playing 12 games for Bern, and was the second-leading scorer for the club's U20 team. He was an assistant captain for Switzerland at the 2010 U18 World Junior Championship. He had no points nor penalty minutes in limited ice time in the NLA. Vermin scored 28 goals with 27 assists in 34 Elite Jr A games and had 59 penalty minutes. Bern was fourth in the regular season and reached the playoff semifinals. In seven U20 playoff games Vermin scored 3 goals with 8 assists and had 4 penalty minutes. One of four players to lead Switzerland with five points at the U18 WJC, he scored 3 goals with 2 assists and was -1. Switzerland finished fifth in the tournament. Vermin was ranked 31st among European skaters in Central Scouting's final rankings but was not selected in the 2010 NHL Draft.
2010-11: Vermin played in 36 games for Bern in his first full Swiss National A league season and represented Switzerland at the 2010 U19 World Junior A Challenge and the 2011 U20 World Junior Championship tournaments. He scored 1 goal with 7 assists and was -1 with 8 penalty minutes in NLA play. Bern reached the playoff semifinals after finishing third and Verman scored 3 goals with 3 assists and was +4 in 11 playoff games. He had 1 goal with 1 assist in four games at the WJAC. Vermin had 1 assist and was -1 with 2 penalty minutes in six games as Switzerland finished fifth in the 2012 WJC. He also played six games for Bern's U20 team; scoring 4 goals with 6 assists. Vermin was ranked 59th amongst European skaters in Central Scouting's final rankings but was not selected in the 2011 NHL Draft.
2011-12: Vermin was tied for third on the team with 11 goals despite skating in only 33 of 50 games for Bern due to a nagging foot injury and played for Switzerland in the 2013 U20 World Junior Championship. He had 11 assists and was +9 as Bern finished fifth in the regular season. In a topsy-turvy post-season, Bern fell to seventh-place Zurich in the NLA Finals. Vermin scored 2 goals with 3 assists and was +2 with 2 penalty minutes in 17 playoff games. He scored 4 goals with 1 assist and was an even plus/minus with 2 penalty minutes in six games for Switzerland, which finished eighth at the WJC. Vermin was ranked 34th amongst European skaters in Central Scouting's final rankings but was not selected in the 2012 NHL Draft.
2012-13: Vermin was the fifth-leading scorer for Bern, trailing only 35-year-old Ivo Ruthemann amongst Swiss-born players, and gained his first international experience skating for Switzerland's national team. Overshadowed by Islanders' leading scorer John Tavares, who had 42 points in 28 games for Bern during the NHL lockout, Vermin scored 13 goals with 22 assists and was +26 with 14 penalty minutes. Bern finished second in the regular season and defeated first-place Fribourg-Gotteron in the playoff finals. Vermin scored 3 goals with 6 assists and was +3 with 8 penalty minutes in 19 playoff games. In two games with Switzerland's men's team he was scoreless and -1 and he was not on the roster at the 2013 IIHF World Championship. Drafted as a 21-year-old in his fourth year of eligibility, Vermin was not among the 130 European skaters in Central Scouting's final rankings when he was selected by Tampa Bay in the seventh round (186th overall) of the 2013 NHL Draft.
ISS in April 2010: "Vermin might have actually been a player who really benefited from his lack of exposure. He's put up great numbers in national team events, and had the opportunity to truly strut his stuff in Belarus, but failed to really impress. Still a valuable asset to his Swiss team, Vermin has a good skill set but failed to blow scouts away. This will likely see him drop to the late rounds and possibly even out of the draft. A good shooter, Vermin isn't able to create the necessary space on his own against the bigger more physical teams, and that above anything else concerns NHL clubs."