This study investigated whether a CBLB inhibitory pentapeptide (Cblin) could be absorbed orally and prevent muscle atrophy. Cblin, found to cross Caco-2 cell monolayers and rat plasma after oral administration, was incorporated into transgenic rice (CbR). Mice fed CbR showed prevention of denervation-induced muscle mass loss and reduced expression of muscle atrophy-related ubiquitin ligases, suggesting CbR as a potential muscle atrophy treatment.