Snapping back to her California roots, the 37-year-old looked every bit the cool mum in a flowing, khaki-green Lisa Marie Fernandez dress and a pair of aviator-style sunglasses.
Meghan wore her long hair loose, which added to the laid-back vibe of her look.
Archie, who spent the day wrapped in his mother's arms, wore a white bodysuit and Meghan swaddled him in a blanket after the match to keep him cosy.
Meghan and Harry's day out with Archie is the first time the family have been out in public together.
The outing comes just days after the royal family celebrated Archie's christening on July 6 at a private service in Windsor.