Endometriosis is the condition in which endometrial glands and mucosa exist outside of the uterus. It affects about 15% of menstruating females and the most frequent location is pelvic cavity. Extrapelvic endometriosis is uncommon. Cutaneous endometriosis is commonly related to previous surgical scars but in rare cases, it can occur spontaneously. We report a case of 42-year-old Korean woman who presented with a skin-colored nodule on the left inguinal area. The patient had no history of previous surgery. Tenderness was the only symptom associated with the lesion and there was no cyclic pain or swelling aggravating during menstrual periods. Histopathology revealed endometrial stroma surrounding glandular structures and hemosiderin-laden macrophages that are compatible for the diagnosis. This case demonstrates that primary inguinal endometriosis can be presented with various clinical aspects and calls for awareness of possibility for inguinal endometriosis in the patients with tender nodules of the inguinal area.