Members of the first-team squad visited a number of wards and presented gifts to hundreds of children.
Celtic has been a long-time supporter of the hospital, which cares for infants and those up to the age of around 13.
Club captain Scott Brown said: "The Club is delighted to have such a strong association with Yorkhill Hospital and as players we really enjoy visiting the kids at Christmas.
"The hospital carries out such brilliant work all year round and it is a great opportunity for us to meet some very deserving children – and, of course, send our best wishes to hospital staff who make such a difference."
The team members – including Charlie Mulgrew, Victor Wanyama and Kelvin Wilson – signed autographs and posed for pictures with patients and staff, and the kids were also given special goodie bags.
David Welch, director of fundraising for Yorkhill Children's Foundation said: "We are very grateful to Celtic Football Club for taking the time to visit all the children at the Royal Hospital for Sick Children.
"The children and their families really do get such a lift from visits like these, especially at this time of year when many families are unfortunately preparing to spend the Christmas period at Yorkhill.
"We hope this visit, and the many more activities we have planned, help make this the best Christmas possible for patients."