Objective: To study the antiseizure drug levels and associated factors in children with breakthrough seizures.Methods: This cross-sectional study conducted at a public hospital from November, 2017 to April, 2019, included 145 children with epilepsy aged 2 to 12 years presenting with breakthrough seizure. Antiseizure drug levels were measured, and the levels were categorized as within, below, and above the reference range.Results: Children with epilepsy receiving sodium valproate, phenytoin and carbamazepine were 111 (73%), 31 (20.4%) and 10 (6.6%), respectively, of which 7 were receiving multiple antiseizure drugs. Drug levels below the reference range were found in 64 (44.1%), within the reference range in 70 (48.3%), and the above reference range in 11 (7.6%) children.Conclusion: Nearly half the children with breakthrough seizures had sub-therapeutic levels, especially those on phenytoin therapy. Drug levels in below therapeutic range were not associated with occurrence of breakthrough seizures.