Over the course of its long and beloved run, Blue Bloods has featured a number of incredible guest stars who left lasting impressions on both the Reagan family and the audience. While the show is known for its steady core cast — Tom Selleck as Commissioner Frank Reagan, Donnie Wahlberg as Detective Danny Reagan, Bridget Moynahan as ADA Erin Reagan, and Will Estes as Officer Jamie Reagan — the guest appearances often brought new layers of emotion, conflict, and excitement that helped shape the series. Here are five famous guest stars who made a real impact on Blue Bloods. One unforgettable guest star was Whoopi Goldberg, who appeared as City Council Speaker Regina Thomas. Her character often clashed with Frank Reagan over issues of police reform, community trust, and political accountability. Goldberg’s performance was powerful, offering a realistic depiction of how politics and policing can collide in modern-day New York City. Her presence added tension and depth, reminding viewers that Blue Bloods isn’t afraid to tackle controversial topics with nuance and intelligence. Next up, Lorraine Bracco made a lasting mark as Mayor Margaret Dutton. Bracco, best known for The Sopranos, brought authority and intensity to her role, making her one of Frank’s toughest political adversaries. Her on-screen chemistry with Tom Selleck was electric — two strong personalities battling for control of the city’s priorities. The dynamic between Frank and Dutton gave fans some of the show’s most compelling scenes, showcasing the push-and-pull between politics and law enforcement leadership. Treat Williams also deserves recognition for his recurring role as Lenny Ross, Frank Reagan’s longtime friend and former partner. Williams’ portrayal of Lenny added a deeply personal touch to Frank’s otherwise stoic character. Lenny’s appearances often explored loyalty, loss, and the cost of service. When Williams passed away in real life, fans were heartbroken, knowing how much he meant to Selleck and the Blue Bloods family. The episodes featuring Lenny Ross became even more meaningful, serving as a tribute to both the character and the actor. Then there was Lou Diamond Phillips, who guest-starred as Luis Delgado, a ruthless cartel leader who became one of Danny Reagan’s most dangerous enemies. Phillips brought charisma and menace to the role, making Delgado both terrifying and strangely fascinating. His storyline with Danny added intensity and high stakes, especially as their cat-and-mouse game turned personal. Phillips’ performance elevated the action side of Blue Bloods while reminding viewers of the emotional cost of being a cop. Finally, Dylan Walsh left a strong impression as Mayor Peter Chase. His portrayal of a pragmatic but sometimes morally gray leader provided a sharp contrast to Frank Reagan’s principles. The tension between the two reflected real-world debates about leadership, ethics, and public service. Walsh’s intelligent and layered performance made Mayor Chase one of the most intriguing political figures to ever face off with Frank. Each of these guest stars not only brought star power but also emotional and narrative weight to the series. They reminded audiences that Blue Bloods is more than a procedural — it’s a story about duty, honor, and the human connections that define those who serve. From political showdowns to personal struggles, these five actors enhanced the world of the Reagans and kept the show feeling fresh and unpredictable. As Blue Bloods came to an end, fans couldn’t help but look back at these unforgettable performances and appreciate how much they contributed to the show’s legacy. Whether it was Whoopi Goldberg challenging Frank’s beliefs, Treat Williams giving him a glimpse of his past, or Lou Diamond Phillips testing Danny’s limits, each guest star left a mark that fans will never forget — proof that even in a show built on family and tradition, sometimes it’s the outsiders who make the biggest impact.