The 32-year old has signed a two-year deal with the swans after his contract with Austrian club Red Bull Salzburg expired at the end of last season.
Tremmel, who has previously played with Hannover, Hertha Berlin and Energie Cottbus, is looking forward to getting started with the Welsh outfit who already have the impressive Michel Vorm and Portuguese gloveman Jose Moreira among its keeping ranks.
"I am delighted to be here as a Swansea player," Tremmel told the club's official website.
"I've been with the club for quite a while on trial, and I already felt part of the squad as everyone here is so welcoming. It is a family club.
"I have also had the chance to see how the team gets on in the Premier League, and I have been impressed by what I have seen.
"I've got a big challenge ahead of me. Of course, I have to be patient because Michel has been playing very well and Jose is also pushing to play.
"However, I feel I have good experience to share from my time playing in the Bundesliga, and that could help us this season.
"But first I need to get my chance, which I will work hard for and I will also be patient.
"I'm just looking forward to getting started officially as a Swansea player."