DREW BARRYMORE is already two-timing her new rock drummer boyfriend with the co-star of her latest movie — while the ink isn’t even dry on her hubby Tom Green’s divorce papers.

And pals say Tom’s green with anger over Drew’s new love!

Drew had been secretly seeing Alec Piro, 26, a drummer for the band Deadsy in L.A., and the relationship seemed so serious they’d been spotted shopping for home furnishings together.

But as soon as the 27-year-old actress left for the Montreal set of her new film “Confessions of a Dangerous Mind,” she fell into the arms of Sam Rockwell, 33, who plays her boyfriend in the flick.

The lovebirds have been warming each other up with passionate embraces and red-hot kisses both on and off the set in frigid Montreal.

And friends say Tom is not only furious with Drew for flaunting the affair in his native Canada, but he now suspects that Sam had eyes for his wife when they worked together on “Charlie’s Angels.”

“Tom is beside himself over the new men in Drew’s life,” a source declared. “It was bad enough when he found out she was making beautiful music with drummer Alec so soon after they split. But Drew throwing herself at Sam has just added insult to injury.

“What’s more, Tom is certain Sam’s had his sights set on winning Drew’s heart for a long time now, even when she was still married to Tom!

“Drew and Sam became fast friends during the making of ‘Charlie’s Angels.’ There was a strong attraction.

“But they didn’t know what to do about it because they were both involved with other people at the time.

“Now Tom’s convinced Sam was just biding his time until her marriage fell apart so he could make his move on Drew.

“As for Alec, he was the man Drew rushed to after her split from Tom. They were popping up all over L.A., even making out in restaurants.

“When he put Drew on a plane to Canada to begin her new role, he had no idea she’d start dating her co-star.

“The bottom line is, after her marriage to Tom failed Drew reevaluated and saw that there were lots of fish in the sea — and she’s got plenty of bait!”

Another source told The ENQUIRER: “Tom and Drew certainly had their problems, chief among them Tom’s jealousy over her booming career and his inability to break out to a bigger audience.

“There was a lot of pressure in the marriage. Tom ultimately couldn’t handle it, and he filed for divorce in December.

“But he says now he would have fought harder to make the marriage work if he knew Drew was going to pick right up with someone else. Tom’s shocked that she was able to rebound so quickly.

“He was sick about Alec — now he’s fuming about Sam!”