The couple began dating in October last year (18), and the "Domino" hitmaker - who is currently on holiday on the Caribbean island of Jamaica - posted a snap of herself relaxing on a sunlounger on the photo-sharing site.
Wearing a black bikini and a black crochet cover up, and laid next to several plates of food, Jessie captioned the snap, "Fresh face trying to be the life of the Pattie (party) I WANT TO LIVE HERE FOREVER."
Channing quickly commented, "Hottest Instagram food model in the game right now."
The singer is in Jamaica to celebrate the 30th birthday of her friend, professional dancer Holly Palmer.
Channing, 38, kept his budding relationship with the British singer quiet on social media, but shared his first post about Jessie on Instagram in November (18).
The actor also showed up backstage at several of Jessie's U.S. concerts, and reportedly took his five-year-old daughter, Everly, to the singer's show in Los Angeles.
The "Bang Bang" hitmaker was then spotted at the debut of Channing's all-male revue show "Magic Mike Live" in London, and even took to her Instagram Story to post a photo from the show and urge followers to check out the production.
Channing returned the favour, and shared a snap from Jessie's gig in the city, praising the singer's emotional performance onstage.
"This woman just poured her heart out on stage at the Royal Albert Hall. Whoever was there got to witness something special. Wow," the "Magic Mike" star wrote. "She went off tonight!"