Unilateral cerebellar agenesis/hypoplasia is defined as total or partial lack of one of the cerebellar hemispheres and it may occur due to etiopathogenetically different mechanisms. Patients usually show cerebellar symptoms, yet patients may occasionally be asymptomatic. This study provides a discussion of 5 cases of unilateral, congenital, rather rare cerebellar agenesis in light of the related literature. Five cases with unilateral cerebellar agenesis/hypoplasia who were seen in the neurosurgery and neurology clinics between April 2010 to September 2013 were evaluated. The youngest patient was a 2-year-old, whereas the oldest one aged 37 years. Three patients were younger than 16 years, whereas 2 patients were older than 16 years; 4 patients were female, whereas 1 patient was male. All patients underwent detailed physical and neurological examinations as well as magnetic resonance imaging. The cerebellar tests of 4 of the patients revealed positive results, whereas one patient was asymptomatic and was diagnosed with cerebellar hypoplasia during examinations performed to find the cause of headaches. Of the 4 patients who had positive cerebellar tests of ataxia, dysdiadochokinesia, and dysmetria, 3 were children and 1 was an adult. Wherever necessary, the patients were subjected to additional examinations of electroencephalography, electromyography, blood tests, abdominal ultrasonography, ophthalmological examination, and psychiatric evaluation. The aim of this study was to point out the fact that unilateral cerebellar agenesis/hypoplasia, which is a rare cerebellar anatomical disorder, may occasionally show minimal clinical cerebellar findings, or may be asymptomatic.