Although AOA1 (ataxia oculomotor apraxia1) is one of the most common causes of autosomal recessive cerebellar ataxias in Japanese population, it is reported from all over the world. The clinical manifestations are similar to ataxia telangiectasia in which non-neurological manifestations are absent and include almost 10% of autosomal recessive cerebellar ataxias. Dysarthria and gait disorder are the most two common and typical manifestations. Oculomotor apraxia is usually seen a few years after the manifestations start. APTX gene on 9p13.3 chromosome is expressed in the cells of all human body tissues and different mutations had been discovered. Here we report two siblings (a girl and a boy) of consanguineous parents visited at Mofid Pediatrics Hospital in 2015, with history of gait ataxia, titubation, tremor, and oculomotor apraxia around five yr old and after that. The brother showed symptoms of disease earlier and more severe than his sister did. After ruling out the common etiologies of progressive ataxia, we did genetic study for AOA1 that showed a homozygous frameshift mutation as c.418_418 del was found. This mutation was not reported before so this was a new mutation in APTX gene.