The Scandal alumna, 46, wore a Michael Kors sheer black floral lace two-piece with a hand-beaded bandeau and tulle rumba skirt.
The costume, which comprises 135,000 recycled sequins, required 1,000 hours to hand-embroider, according to a release.
Washington accessorized the look with a diamond-studded choker and a black Michael Kors blazer draped over her shoulders, as well as Jennifer Behr bobby pins.
Inside, the actress was seen with her husband Nnamdi Asomugha, a rare public outing for the normally quiet couple.
Last year, Washington donned a Tory Burch corseted bodysuit layered with black tulle, as well as Jimmy Choo heels, sheer gloves, and a dazzling collar.
In 2019, when the topic was "Camp: Notes on Fashion," the actress donned a white tank and tiered peach skirt by Tory Burch with the embroidery "negativity is noise" and a Lorraine Schwartz black diamond tiara.
One of Washington's most memorable Met Gala appearances occurred in 2016, when one aspect of her ensemble stood out above all others: a brand-new baby bump.
The red carpet appearance confirmed Washington and her husband, former San Francisco 49ers cornerback Asomugha, were expecting their second child together.
Why choose a star-studded event for her big reveal? Washington told HotGossipNewz at the time that she was following in the footsteps of her and Asomugha's famously reserved approach to discussing their family (they also share daughter Isabelle Amarachi).