The 30-year-old defender has moved to Birmingham on an emergency loan deal until January 2.
The former Nottingham Forest defender joined Rotherham in the summer transfer window, but he has been able to make just eight appearances in all competitions so far this season.
Halford is delighted to be joining Birmingham and has posted the following message on Twitter:
Birmingham, who defeated Charlton Athletic at St. Andrew’s Stadium last weekend, will take on Brighton & Hove Albion away from home in the Championship on Saturday afternoon.
The Blues are sixth in the league table at the moment with 28 points from 17 matches.
Meanwhile, Rotherham currently find themselves second from bottom in the Championship table with 12 points from 17 matches, three points behind 21st-place Huddersfield Town.