The 28-year-old loosehead moved to the island side last summer from Ampthill, having begun his career at Sale.
He follows the likes of Alec Clarey, Richard Barrington and Janco Venter in moving to Saracens from St Peter.
“My goal for the last two years has been to get back into the Premiership and I am incredibly happy and fortunate that I have been given an opportunity here at Saracens,” said Flynn.
“James is a great addition to our squad and we are very pleased to have him on board,” added Saracens director of rugby Mark McCall.
“He has good experience and is very motivated to make the best of this opportunity.”
