Scott Parker, Mark Noble, Danny Gabbidon and Radoslav Kovac visited the children, their families and staff at King George Hospital in Goodmayes.
The players donned Christmas hats and played Santa Claus, handing out gifts and chatting to the young patients, their parents and staff.
One young lad was so pleased with his present of a football, that he held an impromptu kick-around with his heroes in the ward.
Clover ward sister Adele Prue said: "We were really happy to welcome the West Ham players to our ward and can't thank them enough for spending time with your young patients and their families.
"We were delighted with all the gifts and to see how excited the children were to see and meet the players was fantastic - it was a brilliant afternoon."
Parker added: "I think it's really nice we can come down here and see everyone. Hopefully we will put a few smiles on the kid's faces - Christmas is a lovely time of year, but for some children and their families, it's difficult to celebrate it, if you have to spend this in hospital.
"I have three kids myself, so I can only imagine for the families, it must be a worrying time, so hopefully we can give them a little boost and a bit of cheer.
"Here, you put things into perspective. We might not be in the best position football-wise at the moment. But, when you compare it with something like this, you realise that there are more important things to worry about."
