Prior to the 1997-98 season, Simpson was promoted to the head coaching position and guided Zug to the NLA championship in his first year at the helm.

[6] In 2003-04, he guided EVZ to the NLA playoffs, where they fell short in the quarterfinals (4-1 against Bern), despite having former NHL star Claude Lemieux on the team, who had signed with Zug in February 2004 for the remainder of the season.

In his final year at the Zug helm (2007–08), Simpson coached EVZ to another playoff appearance but did not get past the quarterfinals.

[9] Simpson was named head coach of the Swiss national team prior to the 2010 World Championships[10] and remained in that job until 2014.

At the 2010 World Championships, Simpson's team defeated Canada in the preliminary round[11] and made it to the quarterfinals, before falling short to host Germany.

In 2013, Simpson led the Swiss national team to its greatest ever success, a silver medal at the World Championships in Sweden.

[15] In May 2016, after the club had been sold to Hans-Ueli Lehmann and after budget cuts had been announced, Simpson's contract with Kloten was terminated by mutual consent.

On December 4, 2017, Simpson was relieved of his duties as Mannheim head coach due to the team's poor results.

[19] Sean Simpson was named the Head Coach of the Hungary men's national ice hockey team in September 2020 for the next two seasons.