CBS later announced that a spinoff titled Boston Blue was ordered straight to series and would expand the universe with Wahlberg’s character. The actor hasn’t ruled out appearances from his former onscreen family members — with Moynahan the first to be confirmed.

Donnie Wahlberg announced that his Blue Bloods costar Bridget Moynahan will guest star on his spinoff Boston Blue. Wahlberg and Moynahan played siblings Danny Reagan and Erin Reagan on the original Blue Bloods. Moynahan will appear in the premiere of the spinoff and direct another episode later in the season.

Bridget Moynahan will make a special guest appearance as Erin Reagan in the premiere episode of 'Boston Blue.'