Former main cast members Masi Oka and Michelle Borth guest-starred as Dr. Max Bergman and Catherine Rollins, respectively.

[1] The second-most-watched was the penultimate episode, "A ʻohe ia e loaʻa aku, he ulua kapapa no ka moana", with 8.44 million viewers.

While off duty, Junior and Tani witness a murder-for-hire hit on a Chinese triad leader, but the hitman escapes.

Afterwards, Steve asks Quinn to pursue the case further, after no charges are pressed due to lack of evidence.

McGarrett and the task force track down a suspect who might be connected to the stolen list of undercover CIA agents.

The decision was based on several factors, most notably O'Loughlin's recovery from on-set injuries and contracts that were set to end this season.

[39] Exterior shots and outdoor scenes for McGarrett's house were filmed at the Bayer Estate in ʻĀina Haina.

[41] On August 14, 2019, it was announced that Katrina Law was joining the main cast as Quinn Liu, a former staff sergeant with Army CID recently demoted for insubordination.

Garcia and producer Peter Lenkov both confirmed the former's exit, but assured that the door would be open for Jerry to later return as a guest star.

[44] Garcia is set to cross-over onto one of Lenkov's other series MacGyver during its fifth season portraying Jerry Ortega as a guest star.

[32] Chuck Norris made a cameo appearance in the season's penultimate episode as Lee Phillips, a retired sergeant major who is helping his mentee; Lincoln Cole.