The Guard, known as a Conductor in America, blows his whistle when it is time for trains to leave and sits in the brakevan (or a brake coach for passenger trains), where he can apply the brakes in case of an emergency. Guards also have two flags, one red and one green. The green flag means "all set" and the red flag means "danger" or "stop". They often tell the driver what to do.
A guard's uniform is blue trousers, a white shirt, a black tie, with a blue jacket over them, and a blue cap with a black brim and brass plate. In the model series sometimes the brass plate was seen unpainted and remained black.
- Keith Wickham (UK/US; eighteenth season onwards)
- Kōzō Shioya (Japan; Thomas and the Guard, Break Van, and You Can't Win)
- Shinobu Satouchi (Japan; James and the Coaches)
- Katsuji Mori (Japan; The Flying Kipper and Percy's Promise)
- Toshio Kobayashi (Japan; Peter Sam and the Refreshment Lady)
- Takeshi Endo (Japan; Special Funnel)
- Hiroo Sasaki (Japan; Thomas and the Emergency Cable)
- Nobuaki Kanemitsu (Japan; The Adventure Begins)
- Andre Rinaldi (Brazil; Thomas and the Emergency Cable)
- A miniature model of a guard is now on display at the Hara Model Railway Museum.