Williams started performing while a college student, "a part-time job singing at a club, Casino Royal, and I liked it. It was a lot of fun."[8] During those years, she also worked at a telephone company and as a ward clerk at the Chicago Mercy Hospital.
She became a backup vocalist for Stevie Wonder as part of "Wonderlove", lending her vocals on his albums Talking Book, Fulfillingness' First Finale, and Songs in the Key of Life. Williams also appeared on Syreeta Wright's 1974 album Stevie Wonder Presents: Syreeta, Minnie Riperton's 1974 album Perfect Angel and Roberta Flack's 1975 album Feel Like Makin' Love.
She left Wonder in 1975 to sign a deal with Columbia Records and Kalimba Productions. Kalimba was a production company started by Maurice White and Charles Stepney. Williams went on to work on her first studio album with both White and Stepney as its producers. Released in 1976 This Is Niecy rose to Nos. 3 and 33 on the Top R&B/Hip-Hop Albums and Billboard 200 charts. This Is Niecy has also been certified Gold in the United States by the RIAA and silver in the UK by the British Phonographic Industry.[13][14] An album cut, "Free", got to nos. 1, 2 & 25 on the UK Singles, Billboard Hot R&B Songs and Hot 100charts respectively. Another single being "That's What Friends Are For" rose to No. 8 on the UK Singles chart.