The 32-year-old was playing beach football in the surf when her black bikini bottom budged to the right, partially exposing her private parts.
"Paparazzi had some fun! Hope the bikini shots are flattering!" she wrote on her Twitter account.
Menounos, who was seen with actor Michael Chiklis and "The Spin Crowd" stars Jonathan Cheban and Simon Huck, was completely unaware of the incident until one of her followers pointed it out.
"No??!!!! Where did u see? Please tell me you're joking," she responded.
Below are Maria Menounos Bikini Wardrobe Malfunction pics