A 61-year-old man presenting with voiding pain was diagnosed with a bladder tumor by ultrasound in another hospital, and was subsequently referred to our hospital. Cystoscopy showed a nodular tumor and surrounding edematous mucosa in the right wall of the bladder. Initially, we suspected bladder invasion of gastrointestinal malignancy, but abdominal computed tomography, magnetic resonance imaging, and a series of tumor marker tests revealed no abonormalities. We performed transurethral resection of the bladder tumor under the clinical diagnosis of a submucosal tumor originating from the bladder wall. Histopathological examination revealed spindle cell proliferation, which was positively stained with anti-anaplastic lymphoma kinase (ALK) antibody. Based on the findings, the diagnosis of an inflammatory myofibroblastic tumor (IMT) was made. Therefore, we performed partial cystectomy to reduce the risk of local recurrence. The pathological diagnosis was IMT, and the surgical margins were negative. Bladder IMT is a rare disease, and surgical resection is the only recommended treatment. In the literature, if completely resected, the prognosis of patients with bladder IMT is excellent. Also, in the present case, no recurrence has been detected for over 6 months.