The photo showed the couple after a face-painting session.
"This is what it looks like when a little tyrant fairy artist holds you down and makes your face look 'better,'" Tatum wrote
According to PEOPLE, Dewan also shared Instagram Story videos from the face-painting, including an image of Tatum getting a monocle drawn on his face. She also posted a brief clip of Tatum and their 4-year-old daughter Everly playing in a pool.
The face-painting photo appeared after speculation of a split already started online. As PEOPLE notes, Dwan Tatum went to the 2018 Vanity Fair Oscars party by herself. She told Entertainment Tonight that he was "happy to have a night off."
They also both attended the Nickelodeon Kids' Choice Awards last week. Tatum was onstage to promote the new animated movie Smallfoot, while Dewan was in the crowd with Everly.
The couple met during the filming of Step Up in 2006, and married in 2009. They announced their separation in a statement Tatum posted on Twitter and Instagram.
"We have lovingly chosen to separate as a couple. We fell deeply in love so many years ago and have had a magical journey together. Absolutely nothing has changed about how much we love one another, but love is a beautiful adventure that is taking us on different paths for now," the statement read.
"There are no secrets nor salacious events at the root of our decision — just two best-friends realizing it's time to take some space and help each other live the most joyous, fulfilled lives as possible," the couple said. "We are still a family and will always be loving dedicated parents to Everly."
The couple said they will not be commenting on the situation again, and thanked their fans for respecting their privacy.
In an interview with Health Magazine, Dewan said the couple is so busy they need to schedule time together.
"We have not yet scheduled sex, but we do schedule time together, so maybe that is sort of scheduling sex," she said in February. "We will go away for a weekend to get time, but we have no real regimented schedule. I have friends who do this [schedule sex]; it's on the calendar. We've never done that — it might actually be a good idea."