In the urinary system, inflammatory myofibroblastic tumors, mostly located in the kidney, are rare benign spindle cell tumors. In this case, it was aimed to present diagnostic and treatment approach to an inflammatory myofibroblastic tumor of kidney with invasion of the splenic flexure. A 58-year-old female patient who had left flunk pain for one month applied to urology clinic. There was no pathology except tenderness on deep palpation in the left upper quadrant of the abdomen. Laboratory parameters were normal. Computed tomography (CT) was planned for further examination when there was a cystic area adjacent to left kidney in ultrasonography. Tomography revealed a cystic area between left kidney and splenic flexure. Percutaneous catheter was inserted to drain the cyst. When suspicious gastrointestinal content came out during drainage, contrast transition was evaluated by applying contrast from the drain. Contrast transition occurred towards the left colon during the CT scan. Therefore, surgery was planned. The patient underwent nephrectomy, splenectomy, and left colon resection anastomosis with midline incision. One drain was placed in the left pararectal area and the other in the pelvic cavity. The patient was discharged on the postoperative 9th day without complication. In the histopathological evaluation, it was observed that the pathology was compatible with the inflammatory myofibroblastic tumor (IMT). IMT is a rare tumor, and there is no sufficient examination alone for diagnosis. IMT is diagnosed with a multidisciplinary approach that includes clinical findings, laboratory parameters, imaging tools and immunohistochemistry studies.