Fontana was born in Curitiba, Paraná, Brazil, from a family of Italian origin. At just 13 years of age she made it to the finals of the 1996 Elite Model Look. The following year she moved from Brazil to Milan, Italy.
In 1999, at the age of 16, she appeared in the Victoria’s Secret lingerie catalogue. The shoot caused controversy, as Victoria’s Secret stated that they would not use girls younger than 18. Soon after the Victoria’s Secret shoot, she was signed by Versace, Ralph Lauren and Valentino.
In 2008, Fontana made her debut on the Forbes The World’s 15 Top-Earning Models list at place 11, having earned $3 million. She has appeared in the Pirelli Calendar on a number of occasions.