The supermodel, 61, and her rocker, 63, were spotted going to dinner at the Upper East Side eatery Scalinatella on Saturday night.
Then, on Sunday, the pair were all smiles as they emerged from their Tribeca hotel.
Brinkley and Mellencamp were first linked when they were seen dining at the Bowery Hotel in mid-September.
Brinkley’s ex-husband, Billy Joel, even shared the news at a recent concert at Madison Square Garden. “And now she’s dating John Mellencamp!” Joel joked with the crowd after performing his Brinkley-inspired hit “The Longest Time.”