Don’t be blue, Blue Bloods fans. Donnie Wahlberg’s Danny Reagan is carrying the torch on Boston Blue, a spinoff that premiered in October 2025.

The series follows Danny from New York City to Boston, where he cozies up to a family of local law enforcement officials not so unlike his own back home. But it’s his son, Sean, who first brings Danny to Beantown. The series begins with Sean, now an officer in the Boston Police Department, getting injured in a blaze at an office building.

As played by Andrew Terraciano, Sean Reagan was a key character on all 14 seasons of Blue Bloods (2010–2024). It was a surprise, then, when CBS confirmed to Entertainment Weekly last July that Mika Amonsen would take over the role on Boston Blue.

Why was Sean recast for Boston Blue? Here’s everything we know, including what Terraciano and Amonsen have said about the decision.

In October, Boston Blue co-showrunner Brandon Margolis revealed that the choice to recast Sean Reagan was driven by the narrative direction he and the creative team wanted to take the character. Speaking with Variety, Margolis said they “love” Andrew Terraciano’s work on Blue Bloods, but the spinoff represents “a new chapter” for both Sean and Danny.

“It’s not just Sean who has joined the family business as it were and is turning over this new leaf, but it’s also now Danny Reagan is the father to a cop, which he’s never been before,” he continued. “So there are all these new storytelling lanes to explore. It felt like there was an organic opportunity to bring in a new performance with a new energy, to help dramatize that change.”

Margolis reassured fans that “it’s the same character, it’s the same relationship, but it’s also completely different.”

He added, “We love what Mika has brought to Sean, this vulnerability, yet this desire to prove himself. It’s just been great to watch it come to life.”

What has Andrew Terraciano said about the recasting?

In an interview with Us Weekly, Terraciano spoke for the first time about being replaced in the Blue Bloods universe, saying he learned about the recasting on the day he graduated from college in May 2025.

“They had spoken to my mom and she called me [crying],” the actor said, recalling how he and his family were told that producers “might be looking for a different Sean.” Terraciano said Wahlberg called him soon after, which he described as a “really beautiful moment of getting to hear from an old friend but also somebody that you respect so much and have learned so much from.”

He added of working with Wahlberg, “We had such an amazing experience on Blue Bloods that when we talk we’ll always be friends and family first. I’m happy that there are so many other people that now get to share in that amazing experience.”

Despite the recasting, Terraciano said he’s grateful for his years playing Sean Reagan, calling the role “beautiful” and noting that he will “always remember every single line and every day” he spent on set.

He also stressed that Sean is in good hands, saying, “It doesn’t mean for even a second that somebody else can’t go and do something beautiful with it.”

How has Mika Amonsen addressed taking over as Sean Reagan?

In November, Amonsen revealed to Us Weekly that he’s received some “negativity” over the recasting, but added that many fans are embracing the change. “They’re really enjoying the show and they love where it’s going in terms of Sean and that makes me happy,” he said.

Amonsen added that he’s tried to honor the “character that everyone loves” and also Terraciano’s portrayal, while still finding his own version. The actor said the turnaround was quick, as he was cast within a week and “thrown into it quickly.” He dove into Blue Bloods to understand Sean’s development and relationship with Danny by the end of the series,

He further admitted that the early days were stressful. “I definitely felt a ton of pressure at first,” he said. “I felt the pressure to respect an actor before me because I wanted to respect Andrew the best I could.”

Where can I watch Boston Blue?

Boston Blue airs Fridays at 10 p.m. ET on CBS, with new episodes available to stream the next day on Paramount+.