Large ovarian endometriomas may cause severe pressure symptoms and often require surgical management. The laparoscopic approach, although challenging, is feasible and safe when performed by surgeons with advanced minimal access skills, provided that certain rules are respected. We report a case of a 40-year-old, nulliparous patient with a history of endometriosis, low ovarian reserve, and subfertility who presented with a 20-cm left ovarian endometrioma and associated symptoms, managed successfully by laparoscopic cystectomy. Compared to non-excisional surgical methods, endometrioma cystectomy likely causes a more profound decline in post-operative ovarian reserve, which is particularly important in the context of subfertility. We discuss the technical aspects of this challenging procedure, potential alternative approaches, and clinical decision-making as to why cystectomy was preferred.