Prince Philip, 90 years old, was taken to the hospital from the Queen's Sandringham estate in Norfolk late Friday after experiencing chest pains. He had a coronary stent put in after tests found a blocked artery was to blame.
Buckingham Palace says "the Duke of Edinburgh has had a good night" and some members of the Royal Family are expected to visit him at Papworth Hospital near Cambridge later Saturday.
The family is gathering at Sandringham to celebrate Christmas.
The palace said the Queen will attend church as usual Sunday, but it does not know when Philip will be released.