The actress says the two met via mutual friends in the summer of 2013.
Seyfried adds that she enjoys her relationship because she can still be herself.
"I really do have my own identity, both inside and outside the relationship, if that makes any sense. It just feels right. It's also really good to feel OK being alone," she says.
The "While We're Young" star, 29, says her career doesn't help her relationship at all, which is why she's very selective about what roles she chooses.
"But making movies is two solid months of twelve-, fourteen-hour days. I mean, it can ruin your relationship," she says. "And if you make too many bad decisions in a row, people don't come knocking anymore."
Seyfried also revealed she's ready to settle down.
"I want to have kids. And I want them to go to local schools, and there are some really good schools around here," she adds. "I would like my life to be the same as it is now, but with a little less stress and a little less work."