The couple, who are expecting their first child together in July, were quietly snapping photos of a crowd celebrating Carnival, while Smith, 44, was hosting his own party with seven pals.
"Will Smith gets the crowd going!" Kardashian, 32, tweeted with a video showing Smith's balcony above her and the screaming, chanting crowd below. Wearing a long white dress that hugged her curves, the first-time-mom to be showed off her baby bump to fans below.
Rather than attending the 2013 Grammy Awards, West, 35, has been enjoying a romantic getaway with his baby mama, and happened to bump into Smith. The parents-to-be have snapped pictures of their sightseeing adventures -- including a photo of pregnant Kardashian posing like Jesus Christ in front of the famous Christ the Redeemer statue.
But it sounds like the babymoon may already be coming to an end. Kardashian tweeted a photo Monday of Carnival, and wrote, "Bye beautiful Rio!"