Blue Bloods is an American police procedural drama series shown on CBS in the United States and Canada and on Sky Atlantic in the United Kingdom. The series is filmed on location in New York City with occasional references to nearby suburbs. The show premiered on September 24, 2010, with episodes airing on Fridays following CSI: NY before being moved to Wednesdays at 10:00 p.m. Eastern and Pacific time and 9:00 p.m. Central and Mountain time for a four-week tryout. After four weeks, it returned to its original Friday 10:00 p.m. Eastern time slot, and has remained there ever since.

The series follows the Irish-American Reagan family of police officers with the New York City Police Department (NYPD). Francis "Frank" Reagan (Selleck) is the Police Commissioner. He was a U.S. Marine Corps officer and a Vietnam veteran before he joined the NYPD. He is a 9/11 First Responder, a widower whose son Joe was murdered in the line of duty, and has three other adult children-Danny, Erin, and Jamie.

Danny (Donnie Wahlberg) is a top NYPD detective, holding the rank of Detective First Grade, but is sometimes hard-nosed and does not always go by the book. Danny is also a Marine Corps veteran, having served in the Iraq War in Fallujah. Danny's partner at the beginning of the series is Detective First Grade Jackie Curatola (Esposito); however, Kate Lansing (Ketch) became an interim partner early in season three. By episode 13 of the that season, Danny Reagan obtains another interim partner, Candice McElroy (Megan Boone). As of season 3, episode 17, Danny's full-time partner is Detective Maria Baez (Marisa Ramirez).

Erin (Bridget Moynahan) is an assistant district attorney in Manhattan who prosecutes many of the criminals Danny arrests. She is promoted to Deputy Trial Bureau Chief in season three. As unorthodox as her brother Danny is with departmental policy and tactics in making arrests, Erin is conversely legalistic and careful in making sure she gets prosecutions that will stick. The disagreements between the two of them on points of law versus moral and practical considerations generate a lot of dialog for the show.

Jamison "Jamie" Reagan (Will Estes), Frank's youngest child, has a law degree from Harvard, but, after working in a law firm for some period of time, he chose to enter the police force instead. He is graduating from the police academy in the pilot episode. He was initially partnered with Officer Vinny Cruz until Cruz's death at the end of season three. He is currently partnered with Officer Edit (eh-DEET) "Eddie" Janko (Vanessa Ray).

Henry (Len Cariou) is Frank's father, and is called "Pop" by his great-grandchildren. He is former NYPD beat cop who rose through the ranks to Police Commissioner, the position now held by his son Frank. Henry is a United States Marine Corps vet who served in the Korean War. Henry often provides his decades-long perspective to his son, grandchildren and great-grandchildren.

Both Henry's and Frank's wives are deceased. Erin is divorced (her ex-husband, Jack Boyle, has appeared in several episodes) and has one teenage daughter, Nikki (Sami Gayle), who lives with her. Danny is married to Linda (Amy Carlson), an ER nurse. They have two sons, Jack and Sean.

A show trademark is the Sunday Dinner scene around the large table in the Frank/Henry home. The four generations of Reagans gather to eat and discuss their week, which naturally includes current cases or controversies depicted in each episode. The grandchildren often have meaty or moral issue questions which the various adults answer, sometimes with differing viewpoints. The conversation may also include family members ribbing each other, and Henry or Frank dispensing wise advice. Sometimes the conversation breaks down in acrimony due to differing feelings or perspectives between family members on emotional issues, but the family always remains loving and united.

Frank's middle son, Joseph, was an NYPD police detective who died in the line of duty in events that pre-date the series. Joe was involved with the Federal Bureau of Investigation (FBI) investigating a group of corrupt NYPD cops, who were operating within a fraternal organization called the "Blue Templar". The dirty cops murdered Joe when his covert investigation was getting close to naming names.

A running thread through the first season is Jamie's picking up Joe's investigation. The FBI tried to recruit Jamie, but he instead conducted his own covert investigation into Joe's death. Joe's murderers try to kill Jamie by tampering with the brakes on his car, but fail. After the failed hit, Jamie informs Frank, Danny, and grandfather Henry about the results of his informal investigation.

Along with his prosecutor sister Erin, the Reagan family joins together and completes Joe's Blue Templar investigation. After gathering sufficient evidence to obtain arrest warrants, Frank leads a team of police officers, including Danny and Jamie, to execute the warrant. They arrest the corrupt cops while they are having a covert meeting to divide stolen drug money. The group's leader, a detective named Sonny Malevsky, admits to killing Joe Reagan. After his confession, Malevsky commits suicide with his service pistol.

Jamie's field training officer is Sergeant Anthony Renzulli, who is tough but fair with Jamie and thinks Jamie has what it takes to be a great cop. Jamie was engaged to Sydney, a fellow Harvard graduate, who was initially happy for his growing success as a cop, but gradually became upset when realizing the dangers of it. She officially broke off their engagement after Jamie became obsessed with investigating Joe's murder, realizing she can't handle the stress of knowing the risks he takes.