For the event, Meghan wore a bright yellow dress by Brandon Maxwell.
Check out snaps of Meghan and Prince Harry as they toast young leaders.
But they looked as close as always as they held hands arriving for the Your Commonwealth Youth Challenge at Marlborough House. Her makeup was understated, and her hair worn in a low bun.
Social media immediately became split on the video - with some saying the former "Suits" star did not adopt the British accent and others panicking that the new royal was losing her American one.
"To arrive alone to face rows of United Kingdom royals and know the eyes of the entire world are on you could easily have created anxiety signals similar to Harry's but Meghan's upright back, congruent smile and quasi-royal composure suggested she was undaunted by the experience", James said of the Los Angeles-born and raised Royal.
"It really was most thoughtful of you and greatly appreciated by Their Royal Highnesses who send you their very best wishes".
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At the reception, the royal couple met youths who have completed their leadership training provided by the Commonwealth Secretariat in a further step to develop their ideas on the type of Commonwealth they want to see in 2040. As you'll hear in the video below, Meghan's accent slips a touch into Dowager Countess of Grantham territory on a few occasions, particularly in the phrase: "We've all (awwwhhlll) had a great day".
This will mark Harry and Meghan's first official visit to Ireland; they visited Northern Ireland in March, two months before marrying.
Meghan Markle dazzles in yellow as she joins Prince Harry at the "Your Commonwealth" youth reception in London.
They disappeared from the public view for a couple of weeks following their marriage at St. George's Chapel at Windsor Castle on May 19, leading to speculation they had enjoyed a secret and private honeymoon.