Familial Mediterranean fever (FMF) is an autosomal recessive disease affecting populations surrounding the Mediterranean area. In this case report, we report a Japanese female patient with polymyositis (PM) who presented with periodic fever. Genetic analysis revealed that she had compound heterozygous mutations in exon 2 of the MEFV gene (L110P/E148Q/R202Q). Treatment with colchicines (1.0 mg/day) successfully eliminated febrile attack and normalized the elevated levels of neutrophil CD64 expression, leading to the diagnosis of FMF. The association of FMF and PM has not previously been reported, so we discuss this rare association.