Mattner, 31, retired after the round 7 match against Hawthorn due to a debilitating hip condition.
Originally from Ki Ki in South Australia, Mattner played 98 matches with the Adelaide Crows before moving to the Swans at the end of the 2007 season.
Mattner went on to play 124 games for the club - 222 matches in total - including the 2012 premiership, before retiring early this season.
Swans General Manager – Football Dean Moore said the club is pleased Mattner has decided to stay in Sydney to become an assistant coach.
“After Marty retired early in the season, he worked closely with the club’s young players in the reserves, which was a role he performed with great success,” Moore said.
“Marty is a great teacher of the game and he knows what it takes to succeed at the highest level.
“On the field, Marty was an absolute professional and team player, he performed the one-percenters well all the time, and it’s these qualities that make him a great addition to our coaching department.”
After spending six years in Sydney, Mattner said he’s looking forward to remaining in the Harbour City and beginning his new role.
“I’m really excited to be staying with the Swans and thankful for the opportunity to step into a coaching role,” Mattner said.
“During the season when I was injured and retired, that time I spent with the reserves really opened my eyes and confirmed that I wanted to coach.
“It was a great opportunity to see the coaching side of the game, I was really happy with it all and thoroughly enjoyed working closely with the young players.
“I’m really looking forward to this next chapter in my life, it’s a great opportunity to be an assistant coach, and I can’t wait to get back into it for day one of pre-season.”
