A pelvic accessory spleen is uncommon and most patients with this condition are asymptomatic. Ureteral calculus is a common disease and can cause acute abdominal pain. We report a 51‐year‐old male patient who presented at our hospital with acute right lower abdominal pain and gross hematuria. A large mass on the right side of the pelvis was detected on an ultrasound examination, as well as a calculus in the lower segment of the right ureter. Computed tomography angiography showed the presence of a long vascular pedicle with an artery originating from the splenic artery and a vein that joined with the splenic vein. Laparoscopy was carried out and it showed a solid mass covered with omentum on the right lower abdomen. The mass was then removed surgically. Histopathological examination of the resected specimens confirmed splenic tissue. We speculate that the accessory spleen and ureteral calculus caused right lower abdominal pain in our case. However, the ureteral calculus might have played a much more important role in causing acute right lower abdominal pain than the accessory spleen.