The 86-year-old monarch had been due to visit Swansea, Wales, tomorrow to present leeks to soldiers of the Royal Welsh Regiment in honour of Wales' national day.
The palace said the queen was experiencing symptoms of gastroenteritis and her condition would be assessed in the coming days.
The monarch, who last year celebrated 60 years on the throne, is in generally robust health, despite her age.
The palace said today that the queen is spending the weekend as usual at Windsor Castle outside London.
She and her husband, Prince Philip, are due to visit Rome next week.
London: Buckingham Palace says Britain's Queen Elizabeth II has cancelled a public engagement after coming down with a stomach bug.
First Published: Saturday, March 02, 2013, 08:40