The actress showed off her long, lean legs in a Marios Schwarb mini dress with a glossy panel on the bodice. She paired the look with white Bottega Veneta heels.
The couple have remained relatively low profile since they secretly wed in September.
During the premiere Lively posed with a "Croods" character and her sister Robyn, while Ryan stopped for photos with his co-star Emma Stone.
In the film, caveman Grug and his family are forced to leave behind the only world they knows following an earthquake. It opens in theaters March 22.
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