The 21-Day Theory (2025): cast, story & where to watch
2025 · Series · ★ 9
Released in 2025, The 21-Day Theory is a drama series.
What it’s about. Using the 21-Day Theory, a determined woman pursues a wealthy man to prove he's straight—but the truth defies her expectations.
Who’s in it. The 21-Day Theory stars Narikun Ketprapakorn as Pie, Supakorn Saokhor as Boss, Pataraphol Wanlopsiri as Euro and Dom Hetrakul as Barami.
How it landed. With an audience score of 9.0/10, The 21-Day Theory sits among the best-reviewed titles in the catalogue.
Where to watch. Streaming options change often. See the full, country-by-country breakdown on our where to watch The 21-Day Theory page.
If you liked it. Fans of The 21-Day Theory tend to enjoy Breaking Bad, Better Call Saul, Demon Slayer: Kimetsu no Yaiba and Attack on Titan.
Frequently asked
- Where can I watch The 21-Day Theory (2025)?
- Streaming, rental and purchase options for The 21-Day Theory change frequently. Check our where-to-watch page for the latest availability in your country.
- Is The 21-Day Theory worth watching?
- The 21-Day Theory holds an audience score of 9.0 out of 10, and is a strong pick if you enjoy drama. Most viewers rate it highly.
- Who stars in The 21-Day Theory?
- The 21-Day Theory stars Narikun Ketprapakorn, Supakorn Saokhor, Pataraphol Wanlopsiri and Dom Hetrakul.
- When was The 21-Day Theory released?
- The 21-Day Theory was released in 2025.