The midfielder will take in a second stint after helping the Swans to a top-10 Premier League finish and Capital One Cup success last term.
De Guzman scored twice in their Wembley win over Bradford, and his performances last season earned him a first international cap for Holland.
Swansea manager Michael Laudrup questioned the club's lack of business earlier in the summer, but news of the latest deal follows the permanent signings of Jordi Amat and Jose Canas.
Chairman Huw Jenkins said: "Everyone is happy the loan is continuing. Then Jonathan will review his long-term future next summer."
De Guzman spoke warmly of his first year in south Wales in a recent interview.
He said: "We played well in a lot of games. We played good football and it's refreshing playing in a team that has a good football mind.
"I'm very satisfied with what happened. We did very well - we were very creative. We really put Swansea on the map."