When Vernon, who had a loan period at Blackpool last season, became available, it proved an ideal move.
He becomes Blackpool's second summer arrival.
"It's an excellent move for me after five years at Blackpool. I live a couple of miles from the ground and that was a part of my thinking behind the move," said Wellens, who becomes Oldham's seventh close season addition.
"Ronnie Moore is an excellent manager and with the owners of the club looking to bring in new players, I think there are some exciting times ahead at Oldham."