Behr was born in Mill Hill London, of South African Jewish descent. Her father is a partner in London estate agents Behr & Butchoff. Dani Behr is a graduate of the Sylvia Young Theatre School, and was discovered by Pet Shop Boysmanager Tom Watkins, who put her in his female Bros concept, Faith Hope & Charity singing alongside Diana Barrand and future Xpansions star Sally Ann Marsh, signed to the WEA record company. However the band was not successful and Behr moved into television production.
In 1989, Dani Behr had a cameo appearance in Grange Hill and then later was a presenter on the late night Channel 4 music show, The Word, for three years. She went on to feature in over 30 TV shows, including The Big Breakfast,Hotel Babylon, Ice Warriors; and in 2002 the co-presenting role alongside Joe Mace on the first series of the BBC's flagship children's program The Saturday Show. She also provided the voice for the onboard ship's computer (coincidentally) named Dani in the computer game "Privateer 2".
After numerous presenting jobs for shows in the United States, Behr decided to move permanently to Hollywood to begin presenting Extra for NBC. She went on to host several more shows for Fox, NBC/Bravo, VH1, with her biggest hit so far being the 2003 reality show Boy Meets Boy. In between TV, Behr has also presented radio shows for Kiss_100, and has had some minor film acting roles and appeared alongside Kate Winslet, Oprah Winfrey, Glenn Close in the play The Vagina Monologues both in London at The Old Vic and on Broadway at Madison Square Garden.
After marriage and the birth of her two children, Behr attempted a UK television comeback on the 2008 edition of ITV's I'm a Celebrity... Get Me out of Here! where she was the second person to be voted out by the public, on day 12.
On 20 September, 2009 Behr appeared in a new series of the Channel 4 programme Come Dine with Me. This was a celebrity episode in which she appeared with EastEnders actress Laila Morse who plays the part of Big Mo, DJ Dane Bowers and comedian Bobby Davro. Behr came last in the competition (due to ill health she was unable to cook her recipe and had to ask her brother to prepare and serve the food) with first prize (£1,000 given to charity) being awarded to Bowers.