The 36-year-old German goalkeeper left the Liberty Stadium when his previous deal expired at the end of last season but has now been offered a fresh two-year spell by the South wales outfit.
Tremmel was thrilled to put pen to paper for the Swans for who he has played 52 times since arriving from Red Bull Salzburg in 2011.
"It's fantastic to be back at Swansea, this is where I want to be. This is a special club," he told the club's official website.
"I had other options from top-flight clubs in Germany and England, but Swansea is my environment, with my people.
"I know what Swansea is all about, and it's great to be part of the club.
"I've experienced the biggest achievement of my career here in winning the cup, and seeing the club continue to progress is really pleasing for me to see.
"Now I can concentrate on the season ahead and hopefully we can all make this another fantastic campaign for everyone to remember."
BREAKING: @GerryTremmel returns to @SwansOfficial after signing a two-year contract. Welcome back, Gerhard! #swanspic.twitter.com/pFG1uGQiGO
— Swansea City FC (@SwansOfficial) August 11, 2015