The 37-year-old supermodel is set to tie the knot with Kills rocker Jamie Hince on July 2 and has asked the acclaimed fashion photographer - who she has worked with for almost 20 years, most recently for a near-naked photoshoot for Brazil's Vogue magazine - to take pictures at the ceremony and reception.
Mario - who took the official engagement portraits of Prince William and his now-wife Princess Catherine - told iPad newspaper The Daily he wants to "capture the happiness that Kate is going through at the moment."
Among the moments the photographer could be capturing at the wedding reception is a spectacular performance from legendary singer Dame Shirley Bassey after Kate asked her friend if she would provide the entertainment for guests at the reception.
A source said recently: "Kate wanted high-end glamour and good old-fashioned entertainment, and Dame Shirley was the perfect choice. She agreed to play the gig immediately and Kate can't wait for the big day. It will be a real highlight."
It was recently claimed that Kate - who has an eight-year-old daughter, Lila Grace, with ex-boyfriend Jefferson Hack - is planning to turn her wedding into a "small festival", with the celebrations set to continue for several days.
A source said: "Kate wants it to be a party to remember and like a small festival.
"She doesn't want her guests to leave for days so she's making sure there is plenty of food and entertainment. It's a no-expense spared do - thought most of her budget will probably go on alcohol."