Familial hemiplegic migraine (FHM) is a rare autosomal dominant form of migraine with motor aura. We present a case report of a father and son with very similar attacks of hemiplegic migraine and recurrent episodes of accompanying psychoses. Previously, such episodes led to hospitalization and extended clinical examinations, which further worsened the psychoses. Since the episodes were recognized as related to the hemiplegic migraine, a treatment strategy combining sleep and sedation was initiated and progression onto psychosis was almost completely avoided in both father and son. Genetic analyses found no causal gene mutation in the three known FHM genes, suggesting that the phenotype is caused by a yet unidentified mutation.