They were first romantically linked in October 2017, but first met when she hosted Saturday Night Live in 2016.
They have made sporadic public appearances since then, including the 2019 Screen Actors Guild Awards, an NBA game and the Met Gala afterparty.
Speaking with Elle magazine in 2018, the 31-year-old star discussed her changing interest in marriage and motherhood.
"My perspective about kids has changed as I've gotten older. I never babysat or anything. As a teenager, I was like, 'I'm never getting married, I'm never having kids'," she told the magazine.
"And then I got older and I was like, I really want to get married, I really want to have kids."
Before McCary, the La La Land actress dated Andrew Garfield from 2011 – 2015, after meeting on the 2011 set of The Amazing Spider-Man, where they played onscreen couple Peter Parker and Gwen Stacy.
Prior to Garfield, the actress dated Kieran Culkin, the younger brother of Macaulay Culkin, and was previously linked to singer Teddy Geiger.