The "Medicine" singer stunned in a beaded Versace dress with fringe detailing, which also featured a thigh-high split and plunging neckline.
Lopez, 49, completed her look with a matching headpiece and a 129.48 carat Harry Winston purple sapphire and diamond necklace, per E! News.
For Rodriguez's part, the former MLB star, 43, opted for a lilac-colored jacket paired with a white dress shirt, black pants and matching bow-tie.
Before arriving at the gala, which is held on the first Monday of every May in New York City, the "Hustlers" actress shared a snap of the couple en route to the star-studded event.
"Met Ball 2019 here we come...," she captioned a photo of the duo posing for the camera.
The Met Gala holds a special meaning for the couple: they famously made their first official red carpet debut together back in 2017 at the event.
At that time, J-Lo posted a series of photos showing the pair enjoying themselves at the gala — from snapping selfies in the car on the way to the event to blowing kisses at the dinner table.
This year's gala theme, "Camp: Notes on Fashion," was inspired by a seminal 1964 essay by Susan Sontag in which she describes the phenomenon as something that shan't be talked about: "To talk about Camp is therefore to betray it."
The theme is the basis for the Costume Institute's spring exhibition.
The Associated Press contributed to this report.