Nathalie Kelley was born in Lima, Peru, to a Peruvian mother and an Argentine father. She moved to Sydney when she was 2 years old. From a young age, she dreamed about being an actress. She attended North Sydney Girls High School on Sydney's North Shore. When she was 16 she became a salsa dancer, which helped her get the money to finish her education. The "Miss Latin America competition" also earned her a much-needed $1,000, before she took a year off and went to Brazil. The things Kelley saw there prompted her to shun show business and come home to launch herself into a social science degree at the University of New South Wales. She volunteered with Indigenous Australian youth in the inner-city suburb of Redfern before moving to Los Angeles and eventually becoming a film actress.
In August 2011, Kelley signed on in a major recurring role in the second season of the ABC crime drama television series Body of Proof. Kelley appeared as Dani Alvarez in ten episodes and made her final appearance in the episode "Going Viral Part One".
In 2012, Kelley played a vampire princess in the video clip "Luna Llena" from Puerto Rican reggaeton duo Baby Rasta & Gringo. In 2014, she won a regular role in the Lifetime series UnREAL.