After serving in the infantry overseas in World War II, he attended and graduated from the veterinary school at Colorado State University in 1956.

Miller's experience with horses dates to his childhood and included work as a wrangler, trail guide, and rodeo hand.

In 2004, Dr. Miller was inducted into the Hall of Fame by the Western States Horse Expo,[7] and is a recipient of the Bustad Companion Animal Veterinarian of the Year Award in 1995.

[8][9] Miller retired from practice in 1987, in order to devote himself full-time to the teaching of equine behavior and to support the relationship-based horsemanship movement.

[11] Until his death on November 16, 2024 at the age of 97,[12] Miller resided on his ranch in Thousand Oaks, California with his wife, Debby.