Credit: Frank Micelotta/PictureGroup

Despite recent split reports, Sean Penn and Scarlett Johansson put on a happy face to attend Saturday's Guys Choice Awards.

Penn, 50, and Johansson, 26, arrived separately to the Culver City, Calif., awards show taping, but an eyewitness tells Us Weekly the pair came together for photos together backstage.

"[Sean and Scarlett] weren't flirty or anything, but they did seem to get along," says the witness of the couple, who chatted at the green room bar at Sony Pictures Studios. After saying their goodbyes, Penn went to chat with legendary actor Robert DeNiro -- who was surprised when Johansson briefly joined them mid-conversation.

"There was some tension," another backstage source says.

The pair's low-key interaction Saturday is a stark contrast from their prior outings as a couple. See more photos from Spike TV's Guys Choice Awards.

After making their semi-public debut as a couple at Reese Witherspoon's March nuptials, Penn and Johansson were caught packing on the PDA during a romantic trip to Cabo San Lucas, Mexico, and even smooched in plain sight at May's White House Correspondents Dinner -- in the presence of President Barack Obama.

Back in April, the Iron Man 2 actress moved into Penn's $3.8 million home -- where they often ate in, hung out with Penn's kids with ex-wife Robin Wright, and entertained pals like Owen Wilson and Javier Bardem.