However, it is yet to be confirmed whether she will be the maid of honour for the bride, as claimed by some.
Prince Harry also made an appearance on stage during the concert where he delivered a speech about The Queen's Commonwealth Trust, a new which was launched last week - of which His Royal Highness is The President.
The former Suits actress chose to style her hair in a low bun for the occasion, keeping her signature makeup look soft and simple.
Her gold clutch was by Naeem Khan. Fresh from wearing the most flawless floral Self-Portrait dress this morning at an Invictus Games reception, Markle attended the Queen's Birthday Party concert this evening, dressed flawlessly in a Stella McCartney cape dress.
Amir Khan knocks out Lo Greco in 39 seconds on British return
There has never been any doubt about Khan's hand-speed and he caught Lo Greco immediately with a left jab and uppercut in the first few seconds.
Soon, the royal family will grow once again, though this time it will be through a wedding, as Markle and Harry are set to tie the knot on May 19 at St. George's Chapel in Windsor Castle. Kate Middleton, who is expecting her third child any day, did not attend.
Speaking of the big day, rumours are still rife as to who will be the designer to create Meghan's wedding dress - and while we won't find out until she walks down the aisle, fashion experts have been quick to share their predictions with HELLO!.
But the inclusion that may have left your head scratching was the duet with Sting and Shaggy - if someone had told us that the It Wasn't Me singer would one day be booked to perform for the head of British Monarchy we would have laughed you out the room.