The new contract will see Routledge remain with the Swans until the summer of 2016, and is reward for his excellent form since Michael Laudrup took over as manager in the summer.
The 28-year-old found first-team opportunities hard to come by during his first season at the Liberty Stadium, as then-manager Brendan Rodgers put his faith in Nathan Dyer and Scott Sinclair.
But the former Aston Villa, QPR and Newcastle wide man has been a regular starter this term, scoring five goals and revelling in the freedom he has been afforded by Laudrup.