The Hollywood star, 38, and Jessie, 30, are thought to have been seeing each other for a few months.
Eagle-eyed Jessie J fans noticed Channing at two of her recent concerts in Seattle and Salt Lake City.
Over the weekend, they were spotted playing mini golf together in Seattle before he was seen in the audience at her show in Salt Lake City on Monday.
A source told Us Weekly that their relationship is “new, casual and they’re having fun together.”
It’s unclear how the Magic Mike actor and Price Tag singer met, but they once shared an awards stage together.
Back in 2015, Jessie presented Channing with the award for Best Comedic Performance at the MTV Movie Awards.
In early April, Channing and Jenna announced they were splitting following nearly nine years of marriage.
The pair fell in love on the set of 2006 film Step Up. The couple, who are parents to four-year-old daughter Everly, went on to wed in July 2009.
A statement posted on social media at the time read: “Hey world! So… We have something we would like to share.
“First off, it feels odd that we have to share this kind of thing with everyone, but it’s a consequence of the lives we’ve chosen to lead, which we also happen to be deeply grateful for.
“We’re living in an incredible moment in time, but it’s also a time where truth can easily get distorted into ‘alternative facts’ so we want to share the truth so you know that if you didn’t read it here then it’s most certainly fiction.
“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 pair stressed they are “still a family” and would always be “loving dedicated parents” to their young daughter.
“There are no secrets nor salacious events at the root of our decision — just two best-friends realising it’s time to take some space and help each other live the most joyous, fulfilled lives as possible.”
They went on: “We are still a family and will always be loving dedicated parents to Everly. We won’t be commenting beyond this, and we thank you all in advance for respecting our family’s privacy.
The pair hadn’t been pictured at a red carpet event together since the previous September.
Meanwhile, Jessie disappeared from the spotlight after she described herself as ‘one of the greatest singers’ in an interview in 2016.
Responding to a question about why she’s never been asked to perform at the BRIT Awards, she said: “It makes me sad. I’ve done the Grammys, the VMAs … my profile in America is that I’m kind of celebrated as one of the greatest singers and I love it.”
Her last UK single was released in in 2015 and reached number 13 on the official UK chart.
Earlier this year she won a singing competition in China.
“I know a lot of people were shocked when they found out. Like why would I compete in a singing competition… I’m probably the least competitive person I know,” she said when quizzed about why she took part.
“I said yes because I LOVE to do the unexpected and I LOVE to represent the UK and singing everywhere I go. I LOVE to sing. But also it was an opportunity to bridge a gap between two cultures.
“China is an amazing place and so different to anywhere I have ever been. I have never been made to feel more welcomed and loved as I have done here.”