The Real Housewives of New York City star, 44, and Lemonis, a 41-year-old businessman who stars on CNBC's The Profit reality show, were reportedly caught flirting and getting cozy at a Hamptons charity benefit on August 17, Us Weeklyreported.
"They met over the summer and have been seeing each other. He's really smart, successful, and so nice. They really like each other," a source told Us.
In July, Frankel, who previously starred on Bethenny Ever After, mentioned Lemonis on Twitter and it seemed like they had more than a friendship going on.
"Couldn't sleep. Found @marcuslemonis on @TheProfitCNBC I like him & his way of doing business," she told her followers.
Frankel shot down rumors earlier this month that she was dating Modern Family star Eric Stonestreet, however, she joked with Andy Cohen on Watch What Happens Live she was sleeping with Stonestreet that night. Her words were pretty misleading but she found humor in the situation.
Frankel filed for divorce from her estranged husband, Jason Hoppy, in January 2013. Their split was anything but amicable, as they've been dueling in court over their finances ever since.
The third part of The Real Housewives of New York City reunion airs Thursday, August 27 at 9PM ET/PT on Bravo.