Mika Amonsen will replace Andrew Terraciano, who played Sean Reagan throughout the 14-season run of "Blue Bloods."

Donnie Wahlberg Celebrates ‘New Chapter’ at First 'Boston Blue’ Table Read originally appeared on Parade. Donnie Wahlberg celebrated the official start of the Blue Bloods spinoff, Boston Blue, by sharing a photo from the first table read.

Mika Amonsen will play Sean Reagan in the 'Blue Bloods' spinoff, 'Boston Blue,' a role previously played by Andrew Terraciano.