Wagner was born in Los Angeles, California, the daughter of Richard Gregson, a screenwriter and producer, and movie actress Natalie Wood. She is the adopted daughter of actor Robert Wagner. She left Emerson College to pursue an acting career.
She married D.V. DeVincentis on October 11, 2003. She is the half-sister of jewellery maker, Courtney Brooke Wagner, with whom she shares a mother, and stepsister of TV personality and Hollywood reporter, Katie Wagner.
Natasha's birth surname is Gregson, though Robert Wagner adopted her after Natalie Wood's death by drowning in 1981.