Joubert syndrome (JS) is a developmental disorder characterized by cerebellar vermis hypoplasia, hypotonia, psychomotor retardation, abnormal respiratory pattern and abnormal eye movements. The biochemical basis of JS and underlined molecular mechanisms are unknown. Our study presents a case of Joubert syndrome. The diagnosis was made by the clinical symptoms and magnetic resonance imaging of the brain. A two and a half month old female patient presented here is the second child of nonconsanguineous parents. She shows the characteristic findings of the syndrome such as jerky eye movements, episodic tachypnea and cerebellar vermis agenesis. She also has asymmetric head and microcephaly, retinal degeneration, atrial septal defect and myoclonic seizures. Her chromosome composition was 45,XX,-20,-21,+der (20), t(20;21) (q 13.3;q 11.2). This chromosomal abnormality is described for the first time in association with Joubert Syndrome.