The Canadian has spent the last four seasons with Braehead Clan, playing over 200 games for the Glasgow-based club.
Steelers’ boss Paul Thompson said: “It was Important that we looked to get a puck-moving defenseman, but we also wanted a player that had a high compete level and will be defensively sound for us.
“We had four options but I felt that Scott was the most rounded and ticked the boxes for what we were looking for.
“He has been the Clan’s top defenseman and top scoring defenseman for the last four years. His game has improved as the league improved.
“Even though I’ve seen Scott play over the last couple of seasons, it was only when we started to take a real good look at him and watch the videos over and over again did we realise that we really liked what we saw.
“He doesn’t take nights off and that’s important – we like his consistency and want him to bring that game to Sheffield.
“Overall I’m very happy with the mixture and balance of our back end.”
Aarssen added: “I had an incredible four years with Ryan (Finnerty) and the team. We made huge progress as a club in that time.
“If I’m being honest I would have probably returned if it wasn’t for the interest from Sheffield.
“I didn’t think that I would get the opportunity to play for the Steelers, but when the chance came it was an easy decision.
“My time in Braehead though was fantastic and I’d like to thank everyone associated with the club, especially the fans for the way we were treated.
“Sheffield has been “the club” in the UK during my four years over here playing. They are the standard bearer, the club others look up to and aspire to be.
“The deal happened quickly once Thommo made contact with me – there wasn’t much thinking to do.
“This is a new chapter in my career and one I’m looking forward to. This is a dream come true for me.”
(Image permission: Al Goold Photo)