The actor - who played Dr. Cullen in the vampire franchise - popped the question to his actress partner at the top of the Empire State Building in New York on Monday, 16 March.
Jaimie shared a picture from the big moment on Instagram, alongside the caption: "Top of the world with my love @peterfacinelli @empirestatebldg #Love #ES."
Peter, 41, and Jaimie, 31, have been dating since 2012.
They worked together on TV show Nurse Jackie. Jaimie has also appeared in the Thor movies.
Peter was previously married to Beverly Hills 90210 actress Jennie Garth, with whom he was three children: Lola, Fiona and Luca.
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