The Ugly Betty star confirmed the happy news this week (14Jun10) after she was seen sporting a diamond on her ring finger.
But the actress admits her partner didn't surprise her by dropping to one knee with a traditional proposal - the couple talked about marriage and decided on the engagement together.
Speaking ahead of the Edinburgh International Film Festival screening of The Dry Land, she tells WENN, "We'd been together five years so it was more of a conversation (than a proposal)."
Ferrera subsequently kept the news quiet - and most of her friends only found out about the engagement when the news spread online.
She adds, "I didn't see all the sites that picked it up but it's really happy and good news so it's nice. I've been getting a lot of e-mails from my friends who didn't know but they do know now so that's good. Everybody kind of found out at the same time from reading about it!"