The 47-year-old singer and 41-year-old retired MLB star attended the Monday event at the Metropolitan Museum of Art, which honored Japanese label Comme des Garçons and its founder, Rei Kawakubo.
Lopez and Rodriguez were all smiles as they cozied up for photos. The singer turned heads in a blue Valentino gown with a trailing sheer overlay, and accessorized with diamond Harry Winston jewelry
"You're never fully dressed without a smile... #metball2017," she wrote on Instagram.
"It's pretty sexual but, it's cool and I always like something that's a little controversial," the 21-year-old model told Allure.
Lopez and Rodriguez were first linked in March and confirmed their romance the same month. The singer said on The Ellen DeGeneres Show last week that she and Rodriguez met over lunch.
"It's very simple. I was having lunch somewhere and he passed by," she told DeGeneres. "I saw him walk by, and then afterwards, I went outside. For some reason, I just felt like tapping him on the shoulder and saying hi."
"I said, 'Hi, Alex!' and he was like, 'Hi, Jennifer!' and that was it. I mean, more stuff happened, but that's how we met," the star added.