The actress, 40, appears to suffer from a condition known as polydactyly, a congenital physical anomaly in humans that results in extra fingers or toes.
In pictures taken as she walked with her husband and daughter, Pompeo's brown leather flip flops showed she has an extra toe on each foot.
Known for playing the title role of Meredith Grey on the medical drama "Grey's Anatomy,"Pompeo is married to record producer Chris Ivery.
She gave birth to the couple's first daughter, Stella, in September last year.
Pompeo has never publicly spoken about her unusual feet, but the condition is known to have affected a number of high-profile people.