Welcome back, Riley.BCFC
McGree returns to Blues from MLS expansion franchise Charlotte FC on an international loan until January 1 2022.
The versatile midfielder, who has also featured at wing-back, made 15 appearances for Blues during the 2020/21 Sky Bet Championship season following his arrival at the start of October.
He also opened his Blues account last campaign, scoring the opening goal in an away success over Preston North End.
Having put pen to paper on a return to St. Andrew’s, McGree said: "I am delighted to be re-signing for another six months and I can't wait.
"The Gaffer gave me an opportunity and I was enjoying my football. So I hope to continue playing and play well.
"I am settled here at Birmingham, I have got good relationships with the staff and players. It was an easy decision."
Head Coach Lee Bowyer also expressed his delight at McGree's return to the West Midlands.
The Boss told BCFC.com: “Since I’ve come through the door Riley has been great. He’s worked hard, has good quality on the ball and a lovely left foot.
“He’s got a great attitude and he’s a great lad off the pitch too which is important.
“He’s obviously been here for a while so there is no adjustment period. He won’t need time to adjust or settle in.
“He’ll know the way we play and a few of the things we worked on this season. The lads all know him, he knows the lads, so they’ll be on the same wavelength from day one."
Welcome back, Riley.