Aim: To assess risk factors that affect epilepsy prognosis and neurodevelopmental outcome and response to treatment in patients diagnosed with infantile spasm. Methods: In this study, demographics, treatment modalities, etiologies, risk factors affecting neurodevelopmental outcome and epilepsy prognosis were assessed retrospectively at the end of a minimum 24-months follow-up of 104 patients diagnosed with infantile spasm from May 2012 to October 2015. Results: Neonatal seizure during neonatal period, abnormal head circumference, young age at the time of presentation and early gestational age, symptomatic etiology, abnormal initial examination and abnormal development test at the time of diagnosis, consanguinity, the medical center where treatment was started in the second center or beyond and magnetic resonance imaging finding were found to be statistically significant for poor prognosis in terms of neurodevelopment (p < 0.05). Abnormal initial examination and abnormal development test both at the time of diagnosis and at the end of follow-up, consanguineous parents, young age at the time of presentation, symptomatic etiology, a family history of mental retardation and epilepsy were found to be statistically significant for poor prognosis in terms of epilepsy. Administration of adrenocorticotropic hormone (ACTH) for seizure control was statistically significant compared to other antiepileptic drugs (p < 0.05). Conclusion: Infantile spasm is an age-related epileptic encephalopathy, and it was observed that it is still catastrophic, and that the most important factor affecting prognosis of epilepsy is etiology, age at the time of presentation and the medical center where treatment was started in the second center or beyond.