The 43-year-old singer, who plays a cotton field worker in "Lee Daniels' The Butler", said she was spat on by a white person when she was a child, reported E! News.
Carey's father is of Venezuelan and African-American decent while her mother is Irish said it was hard growing up as a biracial child.
"That actually happened to me," she explained, referring to a scene in the movie where a black college student gets spat on by a white woman.
The film is based on the life of Cecil Gaines, an African-American who was an eyewitness to major historical events of the 20th century during his 34-year tenure as a White House butler.
The film, which saw a title war between its producers the Weinstein Company and Warner Bros, has an impressive ensemble cast of Forest Whitaker, Oprah Winfrey, Cuba Gooding Jr, Vanessa Redgrave and Carey among others.