The Saturdays singer and her sister Laura, who is also older than Mollie, stunned in their grey dresses by Two Birds on Saturday (27 July), as they supported their sibling on her big day.
Although the Grecian gowns were the same colour, they each featured different detailing on the straps. While Mollie opted for one strap that wrapped over her shoulder, Laura went for a cute halter neck option.
Mollie - who recently returned from a sun soaked trip to LA - posted the picture on her Instagram page, along with the caption: "Blonde Power!! #KingSisters #Bridesmaids"
Bride Ellen replied: "Best sisters ever :-) gorgeous bridesmaids xxxxx"
The King family watched Ellen tie the knot to longtime boyfriend Harry at a stately home in Surrey and they even put on a few garden games to keep their guests entertained after the ceremony.
Mollie posted a fun photo of herself testing out one of the games and was clearly in deep concentration. She wrote: "Steady Hand King."
The petite blonde songstress also uploaded a special snap of her eldest sister and her new hubby enjoying a dance together that evening. Aww!
What do you think of Mollie's bridesmaid dress? Let us know below, as the best comment from across the website each week wins £50!
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Copyright: WENN Steve Searle