The 'You're Beautiful' hitmaker approached the former Pussycat Dolls star - who he was previously romantically linked to five years ago - after his performance at Drai's club in the W Hollywood Hotel, and they were seen passionately kissing before leaving the Los Angeles venue together.
A source told The Sun newspaper: "They met up straight after James's gig and hit it off like a house on fire. James instantly hit the bar and was buying Jessica drinks and was clearly smitten.
"They only had eyes for each other and were snuggled up in a corner of the bar laughing and joking away all night.
"By the end of the evening and a few drinks later, they were kissing each other's faces off and very touchy feely before leaving together."
Though James, 35, and Jessica are again reported to be dating, the 28-year-old beauty denied they had ever been romantically involved in 2005, insisting she would "never" romance the star.
James - who has previously dated model Petra Nemcova and British socialite Tara Palmer-Tomkinson - has previously spoken about how sex is very important to him and how he also enjoys partying hard after his concerts.
He said: "Sex is as important to me as it is to the next man, and, you know, it's pretty important to him.
"After shows, we like to drink. At four in the morning I'll have anything that's going. After every show we have a party. 85 concerts every year means 85 after-parties in 85 different countries."