It happened around 7:30 p.m. on a farm near Fort Collins.
The man was taken to UCHealth in an unknown condition.
An investigation is underway. This is a developing story. Please check back for updates.
Colorado Parks and Wildlife said it is legal to own a reindeer in Colorado.
Reindeer and caribou are the same animal (Rangifer tarandus) and are a member of the deer family. In Europe, they are called reindeer. In North America, the animals are called caribou if they are wild and reindeer if they are domesticated, the United States Food and Drug Administration said.