Fox, who is set to present during the star-studded show, wowed in an emerald green asymmetrical one sleeve top with an a-line skirt by Azzi & Osta.
Meanwhile, Kelly -- who is among the night's impressive slate of performers -- rocked a white-on-white satiny ensemble that showed off the massive and intricate tattoo covering his torso. He paired the rock star outfit with some silver combat boots.
The couple sparked romance rumors in early June when they were first spotted holding hands and kissing after spending time together at Mr. Furley's Bar in Sherman Oaks, California.
Soon after, Fox appeared opposite Kelly in the steamy music video for his single "Bloody Valentine," and the pair have been working together in Puerto Rico while filming their upcoming movie Midnight in the Switchgrass.
For more on the couple's whirlwind romance, check out the video below.