Carey, who plays a pivotal, supporting role in "Lee Daniels' The Butler," discussed her real-life brush with racism during a cast press conference to promote the film Monday.
After her co-star Yaya DaCosta described the harrowing experience of playing a civil-rights-era Freedom Rider who was spat upon and verbally abused during a sit-in at a coffee-shop counter, Carey revealed: "That actually happened to me.
"And I know people would be in shock and not really want to believe and accept that, but they did [spit on me.] So, it was like that -- right there? -- that was almost the deepest thing to me in the movie because I know what she went through and it happened to be on a bus, as well. It was a school bus, but it was in my face and in the same way," said the 43-year-old native New Yorker.
Carey did not say exactly where or when the incident occurred, or whether the person or people involved were ever dealt with by authorities.
Based on a true story, "The Butler" is about a trusted White House servant, who works for seven presidents from 1952 to 1986, becoming a witness to an extraordinary period of change in U.S. history.
Forest Whitaker plays the title character and Oprah Winfrey plays his wife, a woman who keeps her family together while the butler works long hours looking after some of the most powerful men in the world.
Written by "Recount" and "Game Change" scribe Danny Strong and co-starring Terrence Howard, Cuba Gooding, Jr., Lenny Kravitz, Liev Schreiber, Robin Williams, Alan Rickman, John Cusack, Minka Kelly and James Marsden, "Lee Daniels' The Butler" opens nationwide Aug. 16. It is rated PG-13.
Daniels previously helmed "Precious" and "The Paperboy."