Headkeeper Jack is the head zoo keeper at the Sodor Animal Park.
One Christmas, the boiler that kept the animals in the park warm during the winter failed. Headkeeper Jack asked Thomas to check if the replacement had arrived at Brendam Docks. Due to the snowy weather, it was unlikely to arrive until after Christmas, so it was decided to send the animals to the Sodor Steamworks to keep warm. As a tunnel on the way was blocked, Thomas decided to take them to Tidmouth Sheds instead, however he got stuck in a snowdrift. Headkeeper Jack helped the Park's elephants free Thomas from the drift and accompanied the animals during their stay at Tidmouth.
- Series 14 - Thomas' Tall Friend (does not speak)
- Series 17 - Steamie Stafford and Not Now, Charlie!
- Series 18 - Old Reliable Edward (cameo), Spencer's VIP (cameo), Emily Saves the World (cameo) and Timothy and the Rainbow Truck (cameo)
- Series 19 - The Little Engine Who Raced Ahead (cameo)
- Series 22 - Thomas' Animal Ark
- 2018 - Thomas and Friends: Adventures! (mentioned)
- Matt Wilkinson (UK; Steamie Stafford only)
- Kerry Shale (US; seventeenth series onwards - UK; Not Now, Charlie! onwards)
- Edson Matus (Latin America)
- Nobuaki Kanemitsu (Japan)
- Petri Hanttu (Finland)
- He was not mentioned by name until the twenty-second series.