Season 9

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The ninth season of Hawaii Five-0 premiered on September 28, 2018 on CBS and concluded on May 17, 2019. The season consisted of 25 episodes.

Main

 * Alex O'Loughlin as Commander Steve McGarrett
 * Scott Caan as Detective Danny Williams
 * Ian Anthony Dale as Investigator Adam Noshimuri
 * Meaghan Rath as Officer Tani Rey
 * Jorge Garcia as Jerry Ortega
 * Beulah Koale as Officer Junior Reigns
 * Chi McBride as Captain Lou Grover
 * Taylor Wily as Kamekona Tupuola
 * Kimee Balmilero as Dr. Noelani Cunha
 * Dennis Chun as Sergeant Duke Lukela

Recurring

 * Shawn Anthony Thomsen as Officer Pua Kai
 * Andrew Lawrence as Eric Russo
 * Laura Mellow as Nalani Lukela
 * Cidni Romias as Akela Nakahara
 * Rochelle Aytes as Agent Greer
 * Zach Sulzbach as Charlie Williams
 * Teilor Grubbs as Grace Williams
 * Claire van der Boom as Rachel Hollander

Guest

 * Mark Dacascos as Wo Fat
 * Rosalind Chao as Governor Keiko Mahoe
 * Clifton Powell as Percy Lee Grover Jr.
 * Louis Gossett Jr. as Percy Grover
 * Gladys Knights as Ella Grover
 * Michelle Hurd as Renee Grover
 * Chosen Jacobs as William Grover
 * Eddie Cahill as Carson Rodes
 * Terry O'Quinn as Joe White
 * Michelle Borth as Catherine Rollins
 * Chris Vance as Harry Langford
 * David Keith as Wade Gutches
 * Joan Collins as Amanda Savage
 * Taryn Manning as Mary McGarrett
 * Charlie Saxton as Ricky Schiff
 * Joey Lawrence as Aaron Wright

Trivia

 * On April 18, 2018, CBS renewed the series for a ninth season of H50 along with 10 other series, including the reboot series MacGyver and freshman series S.W.A.T..
 * On May 17, 2018 it was confirmed that Hawaii Five-0 would air in the fall and keep its Friday at 9/8c slot.
 * Ian Anthony Dale is set to return to the series in episode six due to conflicting filming of other CBS television series Salvation in which he is also a series regular.
 * It was later announced that Louis Gossett Jr. and Gladys Knight are set to guest star in an episode as the father and mother respectively of McBride's character, Lou Grover.
 * On November 20, 2018 it was announced that Terry O'Quinn would return in the season's mid-season finale, while on December 4, 2018 it was reported that former main cast member Michelle Borth would return for the mid-season premiere.
 * It was revealed on January 18, 2019 that Joan Collins would be guest starring in an episode as Amanda Savage.
 * On March 6, 2019, it was reported that former main cast member Taryn Manning, who last appeared as a guest star in the sixth season, would be returning as Mary McGarrett.
 * Andy Lawrence's brother Joey who appeared as a guest star in the eighth season is expected to return as a guest star in the two-part season final since his other brother Matthew appeared in episode sixteen.