Introduction: Gastrointestinal tract duplication cysts constitute a rare group of malformation. Patients with presacral mass present with a diagnostic challenge due to the less obvious presentation. Case Report: We report a 7-month-old boy, who presented with constipation and acute intermittent urinary retention. On per-rectal examination, a palpable mass was felt posteriorly with a narrow base, raising a query of pre-sacral/pelvic mass. Ultrasound pelvis revealed a well-defined, rounded oval-shaped cystic mass noted in the center of the lower pelvis, posteriorly. Computed tomography (CT) scan abdomen confirmed a cystic pelvis mass anterior to the rectum causing mass effect. Magnetic resonance imaging (MRI) of the pelvis was done to define its relationship to the sacral spine. A high-intensity lesion was seen on T2 imaging with no spinal involvement. Hence surgical exploration was done, and per operative diagnosis of rectal duplication was confirmed. Postoperatively child was discharged on the fourth post-operative day and doing well on follow-up. Conclusion: We emphasize a complete examination, including per rectal examination in any child presenting with acute urinary retention to exclude pre-sacral masses.