The two musicians were pictured together at the mixing desk, as they listened to music at a studio in Los Angeles over the weekend.
The photo, taken by Jennifer's younger sister Lynda, shows J-Lo and 'Blurred Lines' hitmaker Robin swaying their hands in the air.
Lynda captioned the photo: "Uh oh...walked into the studio to find this: @JLo @robinthicke ...can't be nothing but trouble..."
Playing down any speculation, American Idol judge Jennifer replied: "Just another Sunday afternoon..." with a smiley face on the end.
A make-up free Jennifer wore a backless summer maxi dress, keeping her hair tied up in a bun.
The 44-year-old, who was accompanied by her dancer boyfriend Casper Smart, was also in the studio with American hip-hop artist Big Sean.
Posting a photo to Instagram, Casper said: "In the studio #latesessions with @CORYROONEY @JLo & @BigSean killin the game..!!! #10thAlbum #B.I.G."
Watch J.Lo's music video for 'Papi' below: