The former child stars took home the award for Accessories Designer of the Year for their brand The Row, beating out industry stalwarts Alexander Wang, and Jack McCollough and Lazaro Hernandez for Proenza Schouler.
The fraternal twins, 27, were surprised by their win, telling the audience that they did not prepare a speech before thanking the council for the honor.
Mary-Kate and Ashley both looked gorgeous at the star-studded event in black dresses from their own collection. Both looks featured voluminous long sleeves and belts that drew in the women's teeny waists. Ashley accessorized with a layered silver necklace, drop earrings with green accents, and simple makeup with her hair parted and pulled back. She also carried a zippered clutch and wore black kitten heels.
Mary-Kate mirrored her sister's understated hairstyle and makeup, which was done for both women by celebrity makeup artist Ana Marie Rizzieri with Elizabeth Arden products, and carried the same style of clutch in a different material. She added interest to the black ensemble with green and red drop earrings and a pair of lace-up Christian Louboutin heeled sandals.
Other big winners at the event, attended by such celebs as Heidi Klum, Sophia Bush, Solange Knowles, and Blake Lively, included Rihanna, who was presented with the Fashion Icon Award, Joseph Altuzarra, who was named Womenswear Designer of the Year, and Dao-Yi Chow and Maxwell Osborne, who won the Menswear Designer of the Year award for their brand, Public School.
The famous Full House cuties have been recognized for their design sensibilities at the fashion awards in the past. In 2012 they nabbed the Womenswear Designer of the Year award for The Row.