Paul Caddis, Shane Lowry, Adam Legzdins and Clayton Donaldson popped down to the lift their spirits.
The quartet spent time chatting to patients as well as doctors, nurses and staff at the Bordesley Green facility, who were equally delighted to see them.
Accompanied by Club chaplain Kirk McAtear, the Blues players delivered Christmas gift bags to the children.
And, on behalf of the First Team Squad, they donated a cheque for £1,000 to the Rainbow Trust, a charity which supports seriously ill children, their families and provides vital equipment.
Christine Morrell, Play Specialist at Heartlands Hospital, said: “We were delighted to surprise our young patients with a special visit from their footballing heroes.
"This is a particularly difficult time of year for children and families, especially those who have to stay in hospital over Christmas, and it was wonderful to see so many smiles.
"We are really grateful because visits like this distract children from the treatment they are going through and cheer them up.
“Everyone had a wonderful time and we would like to thank the players for taking the time to visit and for their kind donation.”