The 96-year-old husband of Queen Elizabeth II reportedly fell ill at Windsor after an appearance at Royal Ascot.
The Queen's consort was due to visit the popular attraction next Wednesday, in his role as an honorary fellow of the Zoological Society of London, to present the Prince Philip Award for Contributions to Zoology.
The 96-year-old was said to be in "good spirits" after his two-night hospital stay. The next day, the palace officially announced that he would be stepping down from his royal duties come August.
She traditionally attends each session of the racing event, one of the highlights of the summer season.
The Duke has enjoyed good health throughout much of his life, recovering from a blocked coronary artery in 2011 and a bladder infection in 2012, the latter leading him to miss the majority of the Queen's Diamond Jubilee celebrations and spend a period in hospital.
The queen missed a traditional Christmas church service past year for the first time in decades because of a heavy cold and was hospitalized in March 2013 with symptoms of gastroenteritis.