The 40-year-old star, who plays a crack addict, Paula, in the movie, initially turned down the role because she did not want to perpetuate a negative stereotype about "black women", reported Femalefirst.
"I didn't want to play a crack addict. I feel that there are enough negative portrayals of women in general and black women in particular. I grew up with this really strong mother - really intelligent, powerful, independent, and I've always admired her," Harris told The Daily Telegraph in an interview.
However, the actress is now proud to have portrayed the character of Paula in the film, which has alongside Harris bagged seven nominations at this year's Academy Awards.
"The more layers I have to hide under as a character, the happier I am. So with Paula in 'Moonlight,' despite the tortuous journey to get to her, once I found her was incredibly comfortable on set. Because she is so far removed. She is like the polar opposite to me.