Wilson was born in Sydney, New South Wales, the daughter of Karlene (née White), a caterer, and Darcy Wilson, a former warrant officer. Her parents divorced in 1982. At a young age, she moved and lived a portion of her life in Papua New Guinea. Living there without television or radio, she and her brother learned to entertain themselves putting on private shows for their parents lip synching to Liza Minnelli. This was just a hint of her budding talent to come. Her family moved around from place to place as her father, Darcy Wilson, was in the military special forces. She learned to adapt quickly to each place she moved and was very well liked.

During her teen years she involved herself in sports such as netball and swimming. As a very energetic young woman, her mother was concerned about her being a tomboy, so Peta was sent to deportment classes. While there she was spotted by a modeling agent. Her new career allowed her to live in Europe but Peta had other plans.