Prince William officially passed the baton of Colonel to his wife, addressing her as "Colonel Catherine" in front of the troops.
Kate gave a speech and interacted with two young girls at the event, highlighting her commitment to the regiment.
The parade included presenting sprigs of shamrock and a march-past, during which Kate took the salute.
The day concluded with a visit to the junior ranks dining hall and an official photograph.
This was Kate's first-ever parade as Colonel of the Guards, and she recently made her first official visit to the 1st Battalion Irish Guards.
The King appointed Kate as Colonel of the Irish Guards, while Prince Charles and Queen Camilla were appointed Colonels of other guard battalions.
Kate's visit to the battalion allowed her to learn about their wartime casualty aid, anti-poaching, and anti-landmine efforts, highlighting her dedication to duty and service.