During surgery for otosclerosis, it is common for the surgeon to cut the stapedius tendon. The absence of the stapedius muscle with its tendon is uncommon. in this study, we present a case of the absence of the unilateral stapedius tendon and muscle. During dissections of adult temporal bones, the absence of the stapedius tendon and muscle was found in one case. The tympanic cavity was explored with the help of a surgical microscope. The pyramidal process was not developed. A possible ontogenetic explanation was provided. In the presented case, the cause of the anomaly may be failure of the embryological development of the muscle. Awareness of the variations or anomalies of the stapedius muscle and tendon are important for surgeons who operate upon the tympanic cavity, especially during surgery for otosclerosis.