A spokesman for Birmingham Heartlands Hospital said that 57-year-old Francis was discharged on Monday afternoon.
Francis began his professional career at Blues in 1971 before moving to Nottingham Forest where he went on to score the winning goal in the 1979 European Cup final against Malmo, as well as winning 52 caps for England.
He played in the 1982 World Cup in Spain and had spells at Manchester City, Sampdoria, Atalanta, Rangers, QPR and Sheffield Wednesday.
Francis returned to Blues as manager between 1996 and 2001 after previously managing QPR and Sheffield Wednesday, who he took to the 1993 FA and League Cup finals.
He has been out of the game since leaving Crystal Palace in 2003.