Feline degenerative joint disease causes pain and disability and therefore represents a welfare concern for captive animals. Alternatives to traditional pharmaceutical therapies are gaining popularity and this study aimed to evaluate the efficacy of an egg-shell membrane therapy in captive cheetahs and leopards. Seven animals were treated with SteadfastTM and monitored for radiographic changes (n = 6) and lameness score (n = 7) over a 42 day period. A reduction in lameness was determined over the course of the study (p = 0.01), and improved orthopaedic status detected in 50% (3/6) of animals via radiographic examination. Surprisingly, a negative dose response was detected, whereby animals receiving lower doses exhibited the most marked changes in lameness score. Despite the small sample size and subjective scoring of lameness, this preliminary study demonstrates the need for further investigation into the use of an eggshell membrane-based supplement to improve mobility in captive felids with degenerative joint disease.