The 21-year-old Sports Illustrated model and 33-year-old "Dancing with the Stars" alum were photographed walking hand-in-hand through New York's West Village last week.
The pair was dressed casually and appeared relaxed on their stroll.
A month later, Upton was seen cheering Chmerkovskiy during his opening night performance of "Forever Tango" on Broadway.
But just three weeks ago, Upton told "Extra," "We're just friends," when asked about her relationship with Maks.
Earlier, she told the September issue of Elle magazine, "I really have never had a serious relationship in the industry. I'm just having fun. Obviously I have a very busy schedule at this time in my life, and I don't put relationships as a priority."