Donnie Wahlberg,
Bridget Moynahan,
Will Estes and
Len Cariou are first credited, with
Tom Selleck receiving an "and" billing at the close of the main title sequence. Amy Carlson and Sami Gayle are once again credited as "also starring" within the episodes they appear, whilst Jennifer Esposito entered a dispute with CBS regarding doctor's orders for her to cut back working hours due to her
Coeliac disease. Rather than work around her limited schedule, CBS chose to replace her character this season. As such, Esposito only appears in five episodes, receiving "also starring" billing in all of them. Several guest stars initially replaced Esposito as Danny's temporary partner in story arcs. First up was
Megan Ketch as Detective Kate Lansing.
Megan Boone, from
Law & Order: LA and
The Blacklist appeared in a later arc during the season, although her contract stipulated she had the option to remain as a regular, "also starring" member of the cast should a deal not be reached with Esposito before the fourth season.
Marisa Ramirez then appeared in the final seven episodes as Danny's partner, Det. Maria Baez, before becoming a regular in Season 4.
Main •
Tom Selleck as
New York City Police Commissioner Francis "Frank" Reagan •
Donnie Wahlberg as Detective 1st Grade
Daniel "Danny" Reagan •
Bridget Moynahan as ADA
Erin Reagan •
Will Estes as Officer
Jamison "Jamie" Reagan •
Len Cariou as
New York City Police Commissioner Henry Reagan (Retired) •
Amy Carlson as Linda Reagan •
Sami Gayle as Nicole "Nicky" Reagan-Boyle •
Jennifer Esposito as Detective 1st Grade Jackie Curatola
Recurring •
Megan Ketch as Detective 1st Grade Kate Lansing •
Marisa Ramirez as Detective 1st Grade Maria Baez •
Robert Clohessy as Sergeant Sidney "Sid" Gormley •
Abigail Hawk as Detective 1st Grade Abigail Baker •
Nicholas Turturro as Sergeant Anthony Renzulli •
Peter Hermann as Jack Boyle •
Ato Essandoh as Reverend Darnell Potter • Tony Terraciano as Jack Reagan • Andrew Terraciano as Sean Reagan ==Episodes==