A 42 year-old male presented with right scrotal pain. Ultrasonography and color Doppler sonography revealed a segmental hypoechoic lesion with absent blood flow in the upper part of the right testis. MRI showed a well-defined avascular lesion with rim enhancement suggesting segmental infarction of the right testis. Scrotal pain was improved with conservative treatment, after which MRI revealed a reduction. Segmental infarction of the testis is extremely rare and is difficult to distinguish from testicular torsion and testicular tumor. MRI of the acute scrotum is considered to be important for avoiding unnecessary surgical treatment.