McCarthy, 45, who plays Molly on the show, took to Twitter to express her feelings after broadcasters decided to end the series following its sixth season, reported Us magazine.
"I was shocked and heartbroken when @CBS canceled #MikeAndMolly. I would have shot this show for 50 more years. I'll miss my 2nd family," she wrote.
Show costar Rondi Reed broke the news in a Facebook post. Reed played McCarthy's mother-in-law, Peggy, on the sitcom.
McCarthy has starred opposite Billy Gardell on the series since 2010.
"We have an order for 13 (episodes) and we have not received any word from CBS that there is life past that 13. So we're looking to have closure here on the series," he said.