Thoracic endometriosis is a rare disease characterized by the presence of endometrial tissue within the thoracic cavity. Diagnostic findings, symptom presentations, and treatment methods have varied in defining thoracic endometriosis. Most criteria, however, require spontaneous pneumothorax within 72 hours of menses as the sine qua non for this diagnosis. This report describes a case of spontaneous pneumothorax from thoracic endometriosis in a postpartum female, a unique presentation not yet reported in the literature. The patient clinically improved with oxygen via a non-rebreather mask, and no additional intervention was required as the patient clinically improved on her own. Although there are many theories, there is no single theory that fully explains the pathogenesis of this disease. With further research on this disease, there is hope for a better understanding of the etiology and, subsequently, better treatment options.