Tobey Maguire, Cindy Crawford, Rachel Bilson and Emma Roberts were among the A-list guests at the Chanel event in aid of the Natural Resources Defense Council, which was held at the home of art dealer Larry Gagosian in the Holmby Hills area of the city.
As cocktails were served, guests were surprised with a performance by Smith and Karen O, before being treated to another set by rapper Pharrell Williams during dinner.
Smith also addressed the crowd during the event and urged supporters to keep fighting for conservation issues, saying, "We must as activists not always be ready to win - we always want to win - but we also have to be ready to lose, and lose, and lose, and lose, and keep on fighting. We must be a thorn in their side, and sooner or later, they will bleed."
The Natural Resources Defense Council is one of America's biggest environmental groups and fights to address issues such as climate change and wildlife preservation.