|
A spokesman for the Blues told the club's official website: "A fee has been agreed with Blackburn and the signing should be completed subject to a successful medical."
Johnson has made eight appearances for Rovers this year and can play in midfield or on the wing.
His contract with the Lancashire club was due to expire later this month.
His agent Phil Graham added: "Damien Johnson has agreed to join Birmingham City.
"It's a fresh start for the lad and he's had to look outside the Premiership for regular first-team football.
"He would not have joined Birmingham if he did not think they had a realistic chance of reaching the Premiership.
"They are in with a shot at the play-offs this season, but certainly he is looking to get into the Premiership the season after."