Objective: The differential of an external auditory canal mass is broad. One rare potential cause is a pneumatocele of the tympanic membrane, which has only been described 1 other time in the literature. This report serves to describe the second case of this pathology, including its unique presentation, and benign clinical course. Methods: Case report. Results: A case is discussed in which a pneumatocele of the tympanic membrane was incidentally identified during evaluation of contralateral otologic pathology. The etiology was suspected to be habitual auto-insufflation. After cessation of this practice, the pneumatocele was noted to resolve without further intervention. Conclusion: A tympanic membrane pneumatocele represents a rare cause of an external auditory canal mass. The diagnosis can be made clinically via history, palpation, and otoscopy during auto-insufflation, potentially avoiding further diagnostic testing. Depending on the etiology, resolution can occur after lifestyle modification; however, further interventions may definitively treat the condition if so required.