36-year-old Hudson posted video from her date with the 27-year-old Monday night -- showing the two playfully flirting during a romantic dinner.
At one point, the two were playing with a Snapchat filter that automatically puts animated stars on one of the people in the video ... and that's when J.J. confirmed the two were on an official "date."
"Apparently, the stars belong to the hottest person on the date," Watt said.
No word on how long the two have been dating -- but it appears the two also went on a date on Saturday ... because J.J. posted a pic of wine glasses, roses and cookies for 2 ... but didn't reveal who it was for. Now, it seems we know.
BTW, Hudson has dated superstar athletes in the past -- she was famously connected to Alex Rodriguez back in 2009.