Prince William officially passed on the baton of Colonel to his wife, addressing her as "Colonel Catherine".
The parade included presenting sprigs of shamrock and a march-past where 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 the colonel of the Guards, and she had recently paid her first official visit to the 1st Battalion Irish Guards.
The King made Kate Colonel of the Irish Guards, Prince Charles and Queen Camilla colonels of other guard battalions.
Kate visited the battalion and learnt about the regiment's wartime casualty aid, anti-poaching, and anti-landmine efforts.