Connacht coach Pat Lam confirmed the news to the club's official website on Tuesday.
Since his arrival from Leinster in pre-season, the 24-year-old South African has played in 13 games for Connacht, starting in all but one, and has been instrumental in the team's unbeaten home record.
"We are pleased to say we have extended Quinn Roux’s deal until the end of the season which is great," said Lam. He has very much impressed us. He has impressed everyone since he arrived here - the boys welcomed him, he really enjoys it, and when you tie those factors together, we see the result."
Roux played for Western Province between 2011 and 2012 before joining Leinster in Ireland.