The Wales Grand Slam winner left the Swansea-based region at the end of last season, to join West Country giants Bath.
But he is set to return down the M4 to face his former team-mates when the Ospreys host Bath in a pre-season friendly on August 18.
James spent nine seasons with the RaboDirect PRO12 champions and made a record180 appearance for the region.
Former Scarlets second-row Dominic Day will also return to Wales, following his own move across the boarder.
The match comes a week after the Ospreys training camp in France culminates in a clash with Clermont Auvergne on August 10.