"I'm incredibly happy, I'm incredibly lucky," Quinto said in Out magazine's October issue about his life with Groff.
Quinto did not offer any specific details about their courtship, including when it started.
He did, however, say the romance is a departure from the unsuccessful relationships he had as a result of his father's death when he was 7.
"I found myself in a pattern of being attracted to people who were somehow unavailable, and what I realized was that I was protecting myself because I equated the idea of connection and love with trauma and death," Quinto said in the Out interview. "I had to do a lot of work on the couch to really get to a place where I was able to show up to a relationship with someone who was actually capable of being in one -- and that took a lot of trial and error."