Male breast cancer accounts for less than 1.0% of all breast cancer cases, and its brain metastasis is very rare. We encountered a male patient in whom brain metastasis occurred more than 20 years after the development of breast cancer. The patient was a 78-year-old male who underwent surgery for right breast cancer 24 years ago. Nausea and anorexia had appeared 2 months earlier, and the patient was referred to our department because a brain tumor was suspected on MRI. A 4×4-cm tumorous lesion was observed in the right temporal lobe, and it was heterogeneously enhanced with gadolinium. Suspecting a metastatic brain tumor, tumor resection with craniotomy was performed. Through pathological examination, the patient was diagnosed with brain metastasis of the breast cancer. Whole-brain irradiation was additionally performed. The patient recovered smoothly without neurological deficit and was discharged. No intracranial recurrence was noted on follow-up imaging, but the general condition aggravated, and the patient died after 13 months. Breast cancer in males may metastasize to the brain after a prolonged period in rare cases, for which follow-up examinations by imaging may be necessary.