The eldest of seven children born to an Italian father and an Irish mother, Testino attended the Universidad del Pacifico, the Pontificia Universidad Catolica del Peru and the University of San Diego. In 1982, Testino moved permanently to London.

Testino has shot fashion stories for Vogue, V, Gucci, and Vanity Fair. Celebrity subjects have most famously included Diana, Princess of Wales and her sons. Other subjects have included many actresses such as Kim Basinger, Emma Watson, Cameron Diaz, Gwyneth Paltrow, Julia Roberts, Meg Ryan, and Catherine Zeta-Jones, models such as Claudia Schiffer, Gisele Bündchen, Elizabeth Hurley, and Kate Moss, performers such as Janet Jackson, Madonna, Kylie Minogue and Lady Gaga, and public figures like Baroness Thatcher. Living in London, he continues to photograph the British Royal Family as well as contributing to the image development of Burberry, Gucci, Zara, Michael Kors, Dolce & Gabbana, Estée Lauder, Valentino and Versace. Testino is currently represented exclusively by Art Partner.

Testino's work has been exhibited in numerous galleries and museums around the world, most notably at the National Portrait Gallery in London in 2002.He has also been featured in a number of television documentaries.

On 5 July 2010 an exhibition of Testino's work was launched in London at the Phillips de Pury & Co auction house with a private view that played host to many of the celebrities he is famous for shooting, including Kate Moss and Gwyneth Paltrow.

Testino has been honored for his contributions to many charitable causes and organizations, including The Elton John AIDS Foundation.

Books

• Any Objections?, Phaidon Inc Ltd, 1998. ISBN 0-7148-3816-0
• Front Row Back Stage, Bulfinch Press, 1999. ISBN 0-8212-2632-0
• Alive Bulfinch Press, 2001. ISBN 0-8212-2736-X
• Mario Testino: Portraits, Bulfinch Press, 2002. ISBN 0-8212-2761-0
• Kids, Scriptum Editions, 2003. ISBN 1-902686-34-9
• Visionaire No. 46: Uncensored, Visionaire Publishing, 2005. ISBN 1-888645-54-7
• Let Me In, Taschen, 2007. ISBN 978-3-8228-4416-8
• Lima, Peru, Damiani, 2007. ISBN 8-88943192-X