Selleck mentioned that he was drawn to the project because of the strong pilot script, though he was concerned about becoming involved in an ongoing series because he did not want to compromise his commitment to the Jesse Stone television movies.

[8] In terms of his personal life, Reagan is a widower,[6] and "the family in Blue Bloods is portrayed as deeply Catholic and highly traditional: they meet often for family dinners, always begin the meals with prayers, often explicitly addressing Jesus", but with "no evident concern about traditional Christian teachings on sexual morality", with characters including Reagan having "occasional brief sexual relationships".

Frank is the younger son of Henry (Len Cariou) and Betty Reagan, born in Bay Ridge, Brooklyn, New York in the early 1950s.

Paula visits Frank and reveals the news in an effort to get her son, a young detective in the firearms unit, assigned to a less dangerous precinct.

In "Whistle Blower" (season 2, episode 10), Frank mentions his great-uncle Teddy Reagan, a member of the NYPD Mounted Unit, who spent a cold night in a boxcar with his horse, Dolly, and a flask, waking up much later in Pittsburgh.

[17] His other close friends include Monsignor Walter Donahue, a member of the city archdiocese, and Kevin Kearns (Stacy Keach), the Archbishop of New York.

Due to the chaos, a shootout ensued in which two police officers were wounded and four people from the Westies were killed, including Whitey's wife and grandson.

[24] As Frank began his NYPD service prior to 1994, he is entitled to carry a revolver instead of a semiautomatic pistol as his duty weapon; he prefers a Colt Official Police that originally belonged to his father and grandfather, customized as a FitzGerald Special.

[21] In 2013, Frank is the target of an assassination attempt by Hector Santiago (Omar Maskati), a mentally challenged teenager of the Bitterman housing projects who is tricked by a member of the Los Lordes gang who declared war on the NYPD.

[30] One of Frank's predecessors, "Crooked" Commissioner Connors, served time in a federal prison after his term as PC was completed and left him with more than one mess to clean up, including Officer Thomas Sculley (Warren Kole), one of four patrol officers who, a few months after 9/11, accidentally shot an unarmed Muslim teenager and was acquitted of all charges and allowed by then Commissioner Connors to keep his job.

In 2016, Officer Sculley, who had kept his head down for the last 14 years and made great strides to atone for his horrible rookie mistake, passed the Sergeant's exam with flying colors.

Frank was reluctant to promote him, lest tensions between the citizens and the police grow even worse, and ultimately offers Officer Sculley a choice: transfer to another city (Long Island, Albuquerque, New Mexico, Boulder, Colorado, or San Diego were among the departments Frank talked to) or take his promotion to Sergeant and ride a desk at the NYPD Erie Basin Auto Pound in Brooklyn for the rest of his career.

[33] Frank is nearly served with a vote of no confidence by the NYPD rank and file in 2012 when he publicly apologizes for the accidental shooting of a black man by a rookie patrol officer named Blake (played by Corbin Bleu) instead of waiting for the official report.