We describe a new cast-immobilization protocol to induce muscle atrophy in the lower hindlimb muscles of mice. Bilateral cast immobilization for 2 weeks in a shortened position resulted in a significant loss of muscle size and strength in the soleus and extensor digitorum longus. The availability of a model of cast immobilization in mice may benefit future studies targeting genetic or cell therapy interventions of muscle atrophy in transgenic and mutant mice strains.