The former Addams Family actress has been spotted wearing what looks like an engagement ring in recent months but has only just confirmed that the couple are set to wed.
When asked by Us Weekly about the rumours, she said: "Yeah. We got engaged a couple months back."
Smurfs 2 star Christina, 32, got together with James early last year after they met on her TV show Pan Am, which he worked on as a dolly grip.
The actress was previously engaged to The House Bunny actor Owen Benjamin after they met on the set of the film All's Faire In Love, but the couple split up in 2009. She was later linked to photographer Curtis Buchanan.