"I'd not really been getting a look-in at Palace, I needed to play some games and the manager here wanted a midfielder so it worked out well," he told Plymouth's official website.
"Hopefully we can help each other out. I want to help get some results while I'm down here and then we'll see where it goes."
Argyle boss Paul Sturrock added: "We needed another captain in there and he has captained Wales and many other teams in the past, so there are leadership qualities in him."