Corticobasal syndrome (CBS) is an uncommon movement disorder with a heterogeneous clinical presentation. CBS is generally recognized as a sporadic disorder, although rare familial and isolated genetic cases have been reported among Westerners. We describe a 49-year-old Taiwanese woman that presented with a three-year history of progressive right-hand dystonia, akinetic-rigidity, ideomotor apraxia, and slowness of gait. Her family history included autosomal-dominant parkinsonism with cognitive decline. A genetic analysis revealed a pathogenic heterozygous missense variant, c.902C>T (p.P301L), on exon 10 of the MAPT gene. The antemortem diagnosis of CBS was supported by clinical, structural, brain glucose metabolism, and tau protein molecular positron emission tomography imaging data. These findings expanded the phenotypic spectrum of the MAPT p.P301L mutation. A literature review illustrated the genetic pleiotropy of MAPT mutations in tau-related neurodegenerative disorders. This study was the first to describe a patient in an Asian family with a MAPT mutation that presented as young-onset CBS. Our findings demonstrated the heterogenous phenotypic spectrum of this rare genetic variant. MAPT mutations should be considered in patients with early-onset or familial CBS in the Asian population.