As always, the Duchess looked elegant as she selected a mix of her favourite designers - from British and French to American.
The Duke and Duchess of Cambridge praised the courage of two French army members, who described their injuries and the effects the attacks had on their lives.
For a black tie dinner at the British ambassador's residence that evening, Kate made her third outfit change of the day, into an embellished gown by another of her "go to" designers Jenny Packham.
Kate embodied the St. Patrick's Day spirit and donned a pin of flowing shamrocks on her emerald coat.
The Duchess of Cambridge arrives for a diner at the British Embassy in Paris, France, on 17 March 2017.
The royal couple also posed for photos with the soldiers.
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The aid operation for western Mosul is "far larger and far more complex" than in the east, she said. Hundreds of thousands of civilians are trapped, she warned, and they are in awful danger.
Prince William and his wife, Duchess Kate of Cambridge, are traveling to Paris on Friday.
On day two of their visit, they also attended a "Les Viosins in Action" event, highlighting "the strong ties between the young people of France and the United Kingdom", a tweet from Kensington Palace read.
The mother-of-two paid an apt tribute to France by wearing two of its legacy brands, Chanel - for her dress, handbag and belt - and Cartier jewelry; and she teamed the French luxury labels with a pair of her favorite Tod's fringed leather pumps.
The royal couple are now mid-way through a whirlwind, 24-visit visit to the city and have several engagements on their itinerary this morning, as well as a trip to the Stade du France to watch Wales play France in the Six Nations rugby. We wish William and Kate the best of luck as they continue on their tour of the city of love.
The prince undoubtedly needed to blow off steam before visiting Paris - it's his first official visit to the city where his mother Diana, Princess of Wales, died in a vehicle accident in August 1997.