Every cast member from Blue Bloods who appears in the spin-off series Boston Blue explained

Boston Blue extends the Blue Bloods story and brings back four familiar names from the original run: Danny Reagan, Erin Reagan, Maria Baez, and Sean Reagan. The premiere confirms all four appear, with one role recast for the new setting in Boston.

Boston Blue airs Fridays at 10 pm ET on CBS and streams on Paramount+. Below is a clear rundown, ordered by on-screen impact in the opener, with notes on status changes and what is confirmed versus reportedly planned.

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Danny Reagan returns in Boston Blue

Donnie Wahlberg reprises Detective Danny Reagan, now serving with the Boston Police Department. The episode frames his transfer as tied to a case involving his son Sean, a development reported ahead of launch. Danny teams with Detective Lena Silver, and the story quickly places him inside Boston’s command and community circles.

Danny Reagan in Boston Blue (Image via YouTube/@tvpromos)

The carryover is straightforward, since Danny’s investigative style and family-first priorities were core to Blue Bloods. In Boston Blue, those traits remain visible, only now applied to new partners, new streets, and a city he did not patrol before.

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Erin Reagan appears in Boston Blue

Bridget Moynahan reprises the role of Assistant District Attorney Erin Reagan in the premiere. Erin is shown in Sean’s hospital room and later in a family dinner scene with the Silvers, linking New York and Boston in one hour. The appearance is billed as a special guest appearance, and she is reportedly set to direct an episode of the new series.

On screen, Erin’s role is supportive and procedural, giving Danny a trusted legal mind nearby while he pushes the fire case forward. The episode uses her brief time to keep the Reagan dynamic intact without relocating her job or jurisdiction.

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Maria Baez crosses into Boston Blue

Marisa Ramirez appears as Detective Maria Baez in an early scene that confirms her off-duty relationship with Danny, a thread seeded at the end of Blue Bloods. In the premiere, Baez gets only a short sequence, yet it clarifies that their bond continued after the original series.

Listings describe Baez as recurring, reportedly signaling more chances to connect the shows. Even in a cameo, the character serves a clear purpose, showing that Danny’s personal life did not reset with the new badge and city.

Scene from Boston Blue (Image via YouTube/@tvpromos)

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Sean Reagan returns with a recast

Sean Reagan is back, now portrayed by Mika Amonsen, replacing Andrew Terraciano from Blue Bloods. The premiere opens with Sean in Boston, then he’s injured during a fire, which drives the hour’s investigation and brings the Reagans together in the new setting.

The change was explained by the creators in interviews as a creative choice for a fresh phase of the character’s life, reportedly aiming for a different energy while honoring what came before. Within the episode, Sean’s presence is limited due to the injury, yet his situation powers the plot and motivates Danny’s move and methods.

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What does this mean for Boston Blue

Only four Blue Bloods figures appear in the premiere: Danny Reagan, Erin Reagan, Maria Baez, and Sean Reagan. Frank, Jamie, Eddie, and others are not shown, though several have publicly expressed interest in future appearances. Any such returns remain unconfirmed as of the first episode and should be treated as speculative.

For now, the show uses a focused set of crossovers, reportedly to establish Boston’s new characters while keeping a clear link to the Reagan family and NY ties. That measured approach sets expectations for more cameos later, while the opening hour stands on its own cases and its new unit.

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