The John Wick actor, 59, was seen beaming alongside the visual artist, 54.
Grant wore a satin gown with a plunging neckline and cutouts above the waist, accessorized with a diamond necklace, silver earrings, and a dazzling purple clutch.
She kept her beauty look simple, slicking her hair back into a ponytail with tiny braids.
Reeves likewise dressed to impress, in a navy suit with a dark tie, a grey button-down, and a matching scarf wrapped around his neck.
Reeves and Grant were previously friends and colleagues for nearly a decade before their relationship turned romantic five years ago.