Bath are currently propping up the Zurich Premiership, and will be very pleased to have their workhorse forward back in the squad.
Steve Hansen told the player he could leave to help the struggling side after his passionate performance against England last weekend.
Hansen can exercise the International Rugby Board's rule that allows him to override club commitments the weekend before a Test match.
But with a number of Cardiff players and Gareth Llewellyn of Neath given permission to play in the Welsh Premiership, Hansen has opted to allow Humphreys to leave camp.
Humphreys, who turns 34 on Thursday, said: 'I think it's a special case for me. When they wanted me to help out with Wales, they understood that I had obligations to Bath.
'I asked Steve if I could play for Bath after the match on Saturday and he said `yes'.
Wales' next RBS Six Nations match is against Scotland at Murrayfield on March 8.