The son of a Baptist preacher, Willis developed his singing skills in his father's church. With training in acting and dance, he went to New York and joined the prestigious Negro Ensemble Company. He appeared in many musicals and plays, including the original Broadway production of The Wiz in 1976 and subsequently, the Australian production.
Willis also had written and recorded several albums in the mid-1970s for independent labels and was eventually introduced to French disco producer Jacques Morali. Morali, who dubbed him the "young man with the big voice", approached Willis and said, "I had a dream that you sang lead vocals on my album and it went very, very big".
Willis agreed to sing lead and background vocals under the auspices of Village People, a non-existent concept group which included the hits "San Francisco (You've Got Me)" and "In Hollywood (Everybody is a Star)". The album became a huge hit in the burgeoning disco market. After an offer from Dick Clark for the group to perform on American Bandstand, Morali and Willis were pressed to develop a "real" group around Willis to perform live. They did so by placing an ad in music trade papers for "macho" singers who "could also dance" and "must have a mustache". When performing with the group from 1977 to early 1978, Willis didn't perform in his cop costume. This is seen in the music videos for San Francisco (You've Got Me), In Hollywood (Everybody is a Star) and Macho Man. In the first music video, Willis is seen wearing jeans, a vest, and a hat. In the latter two music videos, he's seen wearing a tank top and shorts. This is also shown on the cover of the album Macho Man where he is wearing a sparkling jumpsuit.
Willis was soon writing songs produced by and co-written with Morali which met with success. The Village People quickly rose to the top of the charts with Willis at the helm scoring numerous chart busters such as "Macho Man", "Y.M.C.A.", "In the Navy", and "Go West".
In 1980, as preparations for a Village People feature film Can't Stop the Music were under way, Willis left the group. Although he does not appear in the movie, he wrote the lyrics for two of the film's songs, "Magic Nights" and "Milkshake". Can't Stop the Music is listed among Hollywood's bigger movie flops.
After Willis departed, Village People never had another hit. In an attempt to "recapture the magic", Morali convinced him to return to the group in 1982 for the album Fox on the Box. The album was never released in the United States. In 1983, Willis left the group for good.
In 2013, Willis appeared on the TV One series Unsung in their two-hour special retrospective on the disco era.
On June 28, 2016, Willis appeared as a contestant on the show "To Tell The Truth" and sang "Y.M.C.A." as the credits rolled.
After leaving Village People, Willis declined offers to record and consistently refused to perform any of his Village People hits. In 2010, he appeared at several Major League Baseball stadiums, performing The Star-Spangled Banner and leading the crowd for the traditional Y.M.C.A. 7th-inning stretch break.
In 1979, Willis recorded a solo album which remained unreleased for over 35 years. The album, Solo Man, was finally released in August 2015.
In 2012, the United States District Court for the Southern District of California ruled that under the provisions of the Copyright Act of 1976, Willis could terminate his copyright transfers to Scorpio Music and Can't Stop Productions, because "a joint author who separately transfers his copyright interest may unilaterally terminate the grant." Willis subsequently held a 33% share of "Go West", "Y.M.C.A.", "In the Navy," and other songs written for Village People and other acts.
In 2015 it was determined that the sole writers of 13 songs were Morali and Willis, and the name Belolo has been removed. Willis now owns 50% of those songs, and subsequently resumed performing his old Village People hits.
In 2017, Willis and Belolo reached an out-of-court settlement, and Willis announced that he would resume his role as lead singer of Village People, with upcoming tours and projects promised.
Willis' life took a downturn after leaving the Village People. He occasionally made headlines for arrests for drug possession. Following an arrest in 2006, he was given probation and ordered into rehab at the Betty Ford Clinic. In 2007, following treatment, Willis made his first statement to the press in more than 25 years, saying, "The nightmare of drug abuse is being lifted from my life... now that the haze of drugs are gone, I'm thinking and seeing clearer now than I have in years... I'm looking forward to living the second part of my life drug-free."
Willis was married to Phylicia Ayers-Allen (whom he met during the run of The Wiz, and who later played Clair Huxtable on The Cosby Show) from 1978 until 1982. He also wrote the lyrics for her album, Josephine Superstar. On November 17, 2007 Willis married a second time; his wife Karen is a lawyer and an executive.