Mieres is expected to make an immediate appearance for his new side this evening when Exeter A face London Irish A.
Head coach Rob Baxter, who saw his side clinch their first European victory away to Bourgoin in Round 2 is delighted to welcome Mieres to the west country.
"In the games we watched him playing for Stade he's a very good tactical kicker and can kick a long way, but also he likes to play a bit of rugby," he said.
"He's a fairly big guy for a 10 so he will carry.
"His all-round game is pretty good, I think he played about 10 games last season for Stade Francais so he's got a bit of pedigree.
"He brings a bit of experience in a position where we felt about two months ago we were a bit thin. As it happens, with Steenson taking a knock on Saturday, his timing's pretty good."
Exeter face compatriots Newcastle Falcons in back-to-back games when the Amlin Challenge Cup returns to action in December.