The 38-year-old took to Instagram to share a snap of the little one with her followers on Wednesday, Aug. 20.
"My heart is in the #Caribbean. #Postcardfromafar," the actress wrote.
In the image, Witherspoon holds her almost 2-year-old son's hand, and looks summer fresh in a white cover-up, hat and sunglasses.
The day before, the star shared another picture from her vacation, with a hint to fans trying to guess her location: "#Postcardfromafar... Guess where?? Hint #2 : where you can catch these guys...,"she captioned the image.
People from around the world are sounding off in the comments with their best bets. But wherever Witherspoon was, there's one thing we know for sure: The woman knows how to vacation in style.