The 24-year-old left Partick Thistle to sign a two-year contract at Tynecastle Park in June but has now moved to Paisley until the end of the season.
He won't play against Hearts tomorrow as there is an agreement in place that he doesn't face his parent club.
Edwards had hoped to establish himself as a first-team regular at Tynecastle but found himself out of the first-team picture with 15 other signings arriving over the summer.
The move to St Mirren will ensure he plays regularly throughout the campaign.