Series 10 of The Dark Railway Series began airing in 2021. The series had ten episodes.
- 101 - Clyde's new life gets off to a rocky start.
- Welcome to the Tunnel - Goose helps with the first major hurdle of the new extension.
- Body Angels - Various engines try to help out their colleagues.
- Tunnel Vision - Progress is being made on the new extension but not everything is going to plan.
- The Road to Bellgrave - Dave's fear of the tunnel puts Bellgrave's reopening at risk.
- Coaled Weight - A coal crisis leads to problems among the fleet.
- Dirty Colossus - Colossus returns to steam, drawing the ire of Clyde.
- Quack Attack - Goose is pressured to recruit Eddie for the DRPS.
- Buckin' Hell - Two visiting engines complete their running-in trials on the DR.
- Barry the Steam Engine - The Dark Railway plays host to some old friends.
- Theo and Otto
- Sir Eustace Missenden
- 257 Squadron
- De la Trip
- Mr. B
- Zeke Dark
- Mr. Dark
- Mr. Smash
- Mr. Chairman
- The Museum Engines (do not speak)
- Colin (mentioned)
- Ed (mentioned)
- Sid (mentioned)
- Repulse (mentioned)
- Caracus Smash (mentioned)
- Maxen (mentioned)
- Lord Stovell (mentioned)
- Leanne (not named; mentioned)
- "Linda" (not named; mentioned)
- Mr. Richardson
- Lord Dexby (does not speak)
- Mr. Stard (does not speak)
- Thomas Dibden as the Narrator and Main Cast
- Anthony Sims as Barry, Buzz and a DRPS Volunteer
- Reilly Cornwall as Goose
- Christian Rasmussen as Mr. B and Buck
- Callum Hancock as Clyde and Warrior
- Andy Stovold as Andy, Stan, Hannah's fireman and Barry's fireman
- Gwion Rhys Davies as Mr. Chairman
- Freddie Veiga-Pires as a BR Man
- Rhys Davies as Gary, Mr. Richardson and Hannah's driver
- Ben Booth as Hammond
- Oliver Pocock as Barry's driver
- This season was produced during the 10th anniversary of Dark DJ Productions. As a result, a number of presentation changes were applied to this season:
- The opening credits use a different opening theme: "101" by Dark DJ. "9" is still used for the closing credits.
- The opening credits text and DDJP watermark are written in gold as opposed to the standard DDJP green.
- This season is confirmed to take place between 1976 and 1978.
- This is the first season to not introduce any permanent engines to the Dark Railway fleet.