Sixty-five year old gentle man presented with constipation for 4 months and bleeding per rectum for one month. Physical examination was unremarkable. Ultrasonography of the abdomen revealed 6 × 9 cms exophytic hypoechoic lesion in pelvis near sigmoid colon. Barium enema study was normal. Colonoscopy showed colitis from anal canal up to 20 cms. Rest of Colon was normal up to Caecum. Contrast enhanced computerized tomography (CT) scan showed lobulated mass lesion in pelvis posteriosuperior to the urinary bladder compressing anterior wall of sigmoid colon. CT scan picture was suggestive of soft tissue tumour in close relation to sigmoid colon or sigmoid mesentery, a diagnosis of small bowel tumor compressing sigmoid colon was made. An exploratory laparotomy was done. On laparotomy, the lobulated tumour seems to be arising from an ileal diverticulum, which was very short in length and situated 50 cms from ileocaecal valve. So diagnosis was soft tissue tumour arising from Meckel's diverticulum. The tumour was adherent to sigmoid colon and part of wall of urinary bladder. There was no evidence of distant spread. Tumour was excised with 3 cm of ileum on either side. End to end anastomosis was done in two layers. Involved area of anterior wall of sigmoid colon was also excised and the defect was closed transversally. Adherent part of the urinary bladder musculature was resected but the bladder mucosa was intact. Postoperative period was uneventful. Postoperatively urinary catheter was retained for 10 days. The pathology report was gastrointestinal stromal tumour (GIST) arising from Meckel's diverticulum. The tumour cells were pleomorphic and 2–3 mitosis were present in 50 high power fields. All margins were negative. Immuno-hisochemistry showed positive reaction for vimentin and C kit. But desmin, actin, S100, and CD 34 were negative.