Background: A pelvic accessory spleen is a rare congenital anomaly. The majority of accessory spleens are found at the splenic hilum. The unusual localization of the pelvic accessory spleen may result in diagnostic uncertainty and may be an exceedingly rare cause of pelvic pain. Case report: This report highlights the case of a pelvic accessory spleen presenting as a symptomatic left adnexal mass due to intermittent torsion around a long vascular pedicle. The mass was removed laparoscopically and histological assessment confirmed the mass to be an accessory spleen. Conclusion: Pelvic accessory spleen is a rare condition and its presence can confound the typical differential diagnosis for pelvic pain. While it is not a typical cause of pelvic pain, this case report presents interesting clinical photographs of a rare pathology and highlights the value of a broad differential diagnosis when there exists diagnostic uncertainty.