Later, the Material Girl shared a picture with the man of the hour himself.
"This Man is a BOSS!!" she gushed. "Thank you Leo for all you do for Mother Earth! Your generosity and care is beyond measure!"
Other A-lists guests at the gala included Madonna's ex, Sean Penn, as well as Jared Leto, Cate Blanchett, Kate Hudson, Tom Hanks, Marion Cotillard, Uma Thurman and Edward Norton.
Proceeds from the event go to DiCaprio's foundation, which offers grants to environmental causes. The foundation is also holding an auction -- raising $30 million so far -- with incredible prizes, including a dinner with both DiCaprio and his longtime pal, Kate Winslet.