The mother and daughter appeared alongside the rest of the royal family in honour of the Queen’s birthday on the Buckingham Palace balcony.
They gathered to watch a flight path take place overhead to mark the occasion.
Kate’s square neck blue dress was a creation by British designer Alexander McQueen.
Despite having given birth less than two months ago, Kate looked very slender in the fitted gown, which nipped in at the waist.
McQueen is a favourite designer of the Duchess of Cambridge, who also opted to wear a pale yellow dress by the designer for the recent royal wedding of Meghan Markle and Prince Harry.
Kate wore a matching fascinator style hat by milliner Juliette Botterill.
The ice blue hat features a silk bow ribbon attached close to the head, with a straw base that sits on the side of the head.
Meanwhile, Princess Charlotte’s wore a puff sleeve blue dress with a white collar, befitting of her young age.
Her hair tied up with a ribbon, Charlotte smiled and laughed while watching the flight path above.
Mother Kate placed her hands gently on her daughter’s shoulders in a touching gesture.
Kate wore a jewellery set by Kiki McDonough for the important occasion.
The matching set consisted of diamond drop earrings and a chain diamond necklace.
Kate and Charlotte were not the only royals to wear blue for the event today.
In fact, the Queen, Kate and Camilla Duchess of Cornwall all matched in blue outfits at the earlier birthday parade.
Meghan Markle, however, stood out in a pink outfit which contrasted with the other female royals.
Her dress is a bespoke design by Venezualen designer Carolina Herrera, who was a favourite of American First Ladies.
Meghan is the newest member of the royals and the Queen’s granddaughter-in-law after her marriage to Prince Harry.
While there is no official rule governing what colours royals must wear at the Trooping the Colour parade, Meghan certainly marked her out compared to the other royals.
The Duchess of Sussex’s dress is a similar pale colour to the nude dress Meghan wore to Prince Charles’ birthday garden party.
While Meghan’s nude dress bared her shoulders, Camilla and Kate chose much more conservative looks.