At the beginning of the '80s she became famous as model, working for top designers such as Armani, Valentino, Ferrè. Nielsen began her acting career in 1985, in Red Sonja. In the same year she met and married Sylvester Stallone the couple acted in two movies together Rocky IV and Cobra before divorcing in 1987.

Nielsen started a music career shortly after her divorce from Stallone in 1987. She released her debut album Every Body Tells A Story in that year and recorded a duet with Austrian pop star Falco called "Body Next To Body" which went to #22 in Germany and #6 in Austria.

In the late 1980s, Marvel Comics approached Nielsen to pose for photographs dressed as the comic book character She-Hulk. She had previously impressed the company with her prior portrayal of their character Red Sonja, and they hoped she would prove just as successful in a new movie venture. The photos did not produce a large amount of investors in the potential film and Marvel was forced to scrap the project. Subsequently she starred in Beverly Hills Cop II, Galaxys and The Double 0 Kid and some European movies.

She appeared on the first season of the Italian version of The Mole (2004) and on the third season of the VH1 reality show The Surreal Life (2004). In the show, Nielsen was seen flirting with Public Enemy rapper Flavor Flav and it was confirmed that they were a couple, even though she was still legally married to Raoul Meyer. The show was such a success that VH1 produced a spin-off reality show called Strange Love, which began airing on the channel on January 9, 2005. Nielsen also appeared with Flav on VH1's Big in '04 Awards. In 2006, she guest-starred on Flav's other reality show, Flavor of Love.

In March 2007, she starred in a new British documentary called Killing Brigitte Nielsen aired on Sky Travel. Her most recent excursion into the world of reality tv, Celebrity Rehab, began airing in January 2008 on VH1.

Nielsen is fluent in Danish, English, Italian and speaks some German.

Nielsen married for the fifth time in March 2005 to bartender Mattia Dessi, who appeared briefly on Strange Love. The marriage was not official, because her divorce from her previous husband was not finalized. On July 8, 2006 they married legally, following her divorce from her previous husband. Her maid of honor was Ivanka Trump