The couple has split after three years together, according to multiple reports. ET has reached out to Petsch and Mills' reps for comment.
Breakup rumors recently sparked after fans noticed the pair posting less and less of each other on social media. Mills, 30, last posted a photo with the Riverdale star, 25, after their trip to Disneyland last December, while her most recent post about him was celebrating his birthday, last April.
Their last red carpet appearance together was at the GLSEN Respect Awards in Los Angeles on Oct. 25, 2019.
The actress spent time with her Riverdale co-stars, Camila Mendes and Lili Reinhart, at the Vanity Fair Oscar party on Feb. 9.
In an August interview with Nylon, Petsch discussed wanting to keep her relationship with Mills more private.
"My relationship [with musician Travis Mills]. I used to share a lot about it online, and now that I don't, people just assume we're no longer together," the actress explained. "But in reality, I realize that it's so much more special and safe if I don't share a lot of it."