Kate Middleton flaunts emerald polka-dot dress on a Christmas visit to kids undergoing treatment

The Duchess of Cambridge stepped out looking festive as she became patron to a children's hospital.

On Tuesday, the Kensington Palace announced that Middleton, 36, was a new patron of the Evelina London Children's Hospital.

The Duchess showed up to the affair along with husband Prince William. While Wiliam wore a suit and blue undercoat, Middleton stunned in her ensemble.

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The mother-of-three wore a dark emerald dress dotted with white polka dots. The upper area had a button-down feature and bowed neckline.

At the end of her long puffed sleeves, Middleton held a green clutch with a fold-over design. She accessorized with long pearl earrings and olive green pumps.

According to PEOPLE, Middleton's outfit goes for £325 and is sold by L.K.Bennett. The British designer was behind the dress and "Dora" clutch. Gianvito Rossi designed the shoes.

The Duchess let her brunette locks out for the visit to the hospital gives children much-needed treatment and support. It caters to those with rare diseases who may also need extra care.

Middleton interacted with the young ones in a series of Christmas-themed activities including arts and crafts and coloring Christmas trees.

Marian Ridley, the hospital's director, said:

"We are absolutely delighted and deeply honored The Duchess of Cambridge has chosen to become our Patron. The Duchess shares our passion for giving children and young people the very best start in life and Her Royal Highness' support will help champion the life-saving care our staff are providing to our patients."

She continued:

"It is a huge pleasure to welcome Their Royal Highnesses back to our hospital and we are absolutely delighted that they are able to join us as we begin to celebrate our milestone 150th anniversary. We are immensely grateful for Their Royal Highnesses' support and we look forward to working closely with The Duchess as our Patron."

After the event, William and Kate went to a charity organization called "The Passage." Founded in 1980, it benefits homeless persons who are going through issues such as drug addiction and mental illness.

Markle's polka-dot dress is reminiscent of another piece she wore to attend Wimbledon last summer.

The Duchess was donned in a white polka-dot dress as she joined her new sister-in-law Meghan Markle. The two watched Serena Williams, Markle's friend, play on center court.

Again in November, Middleton chose to go with polka dots for a family portrait. The long-sleeved dress featured a white bow neckline and long sleeves. Large white buttons came down all the way to its end.

However, the media took note that the navy blue dress was the same one that a guest at Markle's wedding wore in May.

Regardless, in all three instances, the royal member looked stunning and elegant as she typically does.