The 21-Day Theory poster
Where to stream

The 21-Day Theory

9.020251 seasonTV SeriesDrama

Using the 21-Day Theory, a determined woman pursues a wealthy man to prove he's straight—but the truth defies her expectations.

DirectorChainarong Tampong
ProducersSaithip Montrikun Na Ayudhaya·Vorarit Vaijairanai

Where to watch

Not streaming yet
Coming soon

No streaming availability found for The 21-Day Theory anywhere yet.

Seasons & Episodes

E1
Episode 1
Jan 17, 2025
E2
Episode 2
Jan 24, 2025
E3
Episode 3
Jan 31, 2025
E4
Episode 4
Feb 7, 2025

Cast · Directed by Chainarong Tampong

NKNarikun Ketprapakorn
Narikun Ketprapakorn
Pie
SSSupakorn Saokhor
Supakorn Saokhor
Boss
PWPataraphol Wanlopsiri
Pataraphol Wanlopsiri
Euro
DHDom Hetrakul
Dom Hetrakul
Barami

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The 21-Day Theory — streaming FAQ

Which OTT platform streams The 21-Day Theory?

The 21-Day Theory isn't streaming anywhere in United Kingdom yet.

Is The 21-Day Theory on Netflix?

No, The 21-Day Theory is not on Netflix in United Kingdom as of September 2026.

Is The 21-Day Theory on Amazon Prime Video?

No, The 21-Day Theory isn't on Amazon Prime Video in United Kingdom right now.

Where can I watch The 21-Day Theory for free?

The 21-Day Theory isn't streaming in United Kingdom yet, so there's no way to watch it free at the moment.

How many seasons are in The 21-Day Theory?

The 21-Day Theory has 1 season in total (4 episodes). The series concluded in 2025.

Are all episodes of The 21-Day Theory out yet?

Yes — all 4 episodes across 1 season of The 21-Day Theory are out and available to stream.

Is there a Season 2 of The 21-Day Theory?

No — The 21-Day Theory ended after 1 season, so there is no Season 2.

Is The 21-Day Theory based on a true story?

Yes — The 21-Day Theory is based on true events, dramatising real people and events (some details may be fictionalised for the screen).