Non-traumatic visual impairment is rare in the pediatric population, but early diagnosis and treatment of the cause is crucial to prevent long-term consequences affecting children's neurocognitive development. The authors aim to determine the most common causes of non-traumatic visual impairment in pediatric patients according to age groups by magnetic resonance imaging (MRI). Images of patients who underwent contrast-enhanced cranial and orbital MRI for new-onset visual impairment between June 2019 and June 2022 were retrospectively reviewed. MRI findings were categorized as tumors, idiopathic intracranial hypertension, demyelinating disorders, infections, isolated optic neuritis, and others. The patients were grouped according to age as preschoolers, schoolchildren, and adolescents. Demographic features of patients and MRI findings were collected and compared among age groups. One hundred seventeen of the 238 patients had pathologic MRI findings. The most common pathologies were tumors (26.4%), idiopathic intracranial hypertension (24.7%), demyelinating disorders (18.8%), infections (11.1%), and isolated optic neuritis (7.6%). Tumors (69.2%) in preschool children, idiopathic intracranial hypertension (36.3%) in schoolchildren, and demyelinating disorders (32.7%) in adolescents were the most common cause of vision impairment by age group. Children with acute vision impairment could have severe pathologies. Tumors in preschool children, idiopathic intracranial hypertension in schoolchildren, and demyelinating disorders in adolescents were the most common causes of new-onset vision impairment detected with MRI. Because of the difficulty of performing optimal ophthalmologic and neurologic examinations, especially in young children, cranial and orbital MRI should be considered to detect life-threatening pathologies.