The actress agreed to wear the gown, designed by Stella McCartney, to the Metropolitan Museum of Art's glitzy Met Ball as part of Colin Firth's wife Livia's Green Carpet Challenge (GCC).
In her Vogue.com blog, Livia writes, "They don't come more dazzling than Ms Cameron Diaz who last night joined the Green Carpet Challenge at the Met Ball wearing Stella McCartney.
"This glittering dress was made from organic silk in collaboration with the GCC. On to this, Stella added thousands of beautiful glass beads and crystal chain, which gave us a new challenge for the future as we work on traceability and sourcing embellished materials. After the insight we've had with fairtrade and traceable jewellery and gemstones, this is something I can't wait to get started on!
"To have an artist such as Cameron joining the GCC is a huge vote of confidence and extremely exciting."