Posterior cranial fossa (PCF) tumors in childhood are often associated with ataxia as well as other motor, neurobehavioral and linguistic impairment. The use of a reliable outcome measure is mandatory to evaluate the severity of impairment and monitor rehabilitation effectiveness. The aim of this work is to explore the validity of the Scale for the Assessment and Rating of Ataxia (SARA) in pediatric subjects with ataxia secondary to PCF tumor resection and evaluate the influence of age and comorbidities. Seventy eight patients (3–18 years) were recruited in 5 centers from 2016 to 2018. The age effect on SARA was analyzed by correlating total SARA scores and item scores with age and gradually excluding youngest subjects. The comorbidity effect was evaluated by comparing the ataxia-only group vs a group of subjects with ataxia + dysfunction of cranial nerves or cerebellar mutism (CM) and a group of patients with ataxia + hemiparesis. Several negative correlations between SARA scores and age were found under age 9. Differences between ataxia-only group and the other two groups were closely associated with specific comorbidities (e.g. speech disturbance in cranial nerves or CM group (p value < 0.001) and gait, stance, sitting and finger chase in the hemiparetic group (mean p value 0.022)).