The young princess, who was dressed in a light pink dress, was held in the Duchess of Cambridge’s arms as the royal family stood before waiting crowds outside the palace.
Prince George was also present on the balcony, with Prince William carrying him to join his little sister before they stood beside Her Majesty.
The young Prince looked delighted as 29 aircrafts, including a spitfire, hurricane and the Red Arrows, took part in an RAF flypast over Buckingham Palace.
Today’s Trooping the Colour parade, held as part of the Queen’s 90th birthday celebrations, is the first time both young royals have been out on the balcony at the palace together.
