The Diplomat season 4: Release date and latest news

*Warning - contains full spoilers for all eight episodes of The Diplomat season 3*

Acclaimed political thriller The Diplomat ended its third season on a chilling note, as Keri Russell's Kate began questioning whether she could trust her husband, Rufus Sewell's Hal, in his new position as Vice President.

Allison Janney's President Grace Penn, had made a decision to take a powerful weapon from a Russian sub in British waters, without informing Rory Kinnear's Prime Minister Nicol Trowbridge - potentially putting both the UK and the US in danger.

Now, the series is about to return, with Janney and her The West Wing co-star Bradley Whitford, who plays Grace's husband Todd, becoming series regulars in the cast.

But just when will the new episodes arrive on Netflix, what will the new season be about and who else is returning to star?

Read on for everything you need to know about The Diplomat season 4.

Will there be The Diplomat season 4?

There will! In fact, Netflix has shown such confidence in the series that it renewed it back in May 2025, five months before season 3 even debuted.

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When will The Diplomat season 4 be released?

We now know that The Diplomat season 4 will officially arrive on Netflix on 15 October 2026.

This means it is arriving exactly a year after season 3, which itself came 12 months on from season 2. It will once again be made up of eight episodes.

What will The Diplomat season 4 be about?

The official synopsis for season 4 says that it will see "two marriages threaten to eat each other alive".

The synopsis continues: "One catastrophic moment shatters the fragile peace Kate Wyler brokered between the US and UK, as well as the crumbling marriage she’s trying to save.

While she fights to stem the bleeding, President Grace Penn and VP Hal Wyler’s conspiracy to steal Russia’s most powerful weapon hurtles the United States toward war. Kate and Todd, at best an uneasy pair, unite to stop the Grace-Hal alliance from upending the balance of power abroad and at home."

Season 3 ended on a massive cliffhanger, which saw Kate realise that Hal and Grace had authorised an American sub to take The Poseidon, a hugely powerful salted bomb, from a Russian sub in British waters.

Kate noted that should the Brits find out, they would consider it an act of war. Meanwhile, if the Russians found out, they would likely believe it was the Brits that took it, and could even attack the UK as a response.

The cliffhanger also saw Kate and Todd question the closeness of Hal and Grace's relationship, just as Kate looked to rekindle her marriage to Hal. Are they just trusting colleagues, or is there something else going on?

It seems likely these questions will be further posed in season 4, while Kate also continues to choose between Hal and her new boyfriend, Callum. Plus, there's still the feelings she shares with British Foreign Secretary Austin Dennison, despite him now being a married man.

Who will return to star in The Diplomat season 4?

Keri Russell and Rufus Sewell will of course be back as Kate and Hal Wyler in season 4, and that they will be joined once again by Allison Janney and Bradley Whitford, who have been promoted to series regulars for the new run.

When that was announced, creator Debora Cahn said in a statement: "Working with Allison and Brad, watching them together again, and the off-the-charts foursome that is them with Keri and Rufus… It’s an insane bag of candy. Our expectations were high, and it blew right past them."

Meanwhile, we are expecting the rest of the central cast of the series to all be back as well, including Ato Essandoh, Ali Ahn and Rory Kinnear.

The currently confirmed cast members for The Diplomat season 4 includes:

• Keri Russell as Kate Wyler
• Rufus Sewell as Hal Wyler
• Ato Essandoh as Stuart Hayford
• Ali Ahn as Eidra Park
• Nana Mensah as Billie Appiah
• Rory Kinnear as Prime Minister Nicol Trowbridge
• Bradley Whitford as Todd Penn
• Allison Janney as Vice President Grace Penn

Is there a trailer for The Diplomat season 4?

There is! You can watch the thrilling trailer for The Diplomat season 4 right here now.

The Diplomat season 4 will stream on Netflix from 15 October 2026. You can sign up to Netflix from £7.99 a month. Netflix is also available on Sky TV and Virgin Media.

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