BACKGROUND: ATX-FGF/SCA27A has been exclusively associated with heterozygous variants in the FGF14 gene, presenting with postural tremor, slowly progressive cerebellar ataxia, and psychiatric and behavioral disturbances. OBJECTIVES: This study describes the first case of ATX-FGF/SCA27A linked to a biallelic frameshift variant in the FGF14 gene. METHODS: Whole-exome sequencing (WES) was conducted using the Illumina NovaSeq 6000 platform, and the identified variant was confirmed using Sanger sequencing. RESULTS: We report the first case of autosomal recessive FGF14-related cerebellar ataxia caused by a c.75del variant resulting in p.Leu26Serfs*51 truncation of the FGF14 protein. This variant was found in a patient born to consanguineous parents and presented with a complex congenital nonprogressive cerebellar disorder accompanied by neurodevelopmental delay, intellectual disability, and prominent drug-responsive paroxysmal non-kinesigenic dyskinesia. Segregation analysis confirmed that the homozygous variant was inherited from heterozygous parents who developed mild gait ataxia and tremor in their 40s. CONCLUSIONS: Biallelic loss-of-function variants in FGF14 are a rare cause of inherited cerebellar ataxia and expand the current genetic spectrum of ATX-FGF14. © 2024 International Parkinson and Movement Disorder Society.