Objective: Infections are one of the most common causes of febrile seizure and a history of frequent upper respiratory tract infections is an indicator of low immunoglobulin (Ig) levels in children. We aimed to evaluate Ig values in children with a history of frequent infection who had febrile seizures for the first time to determine the frequency of Ig deficiency diagnosed in the first febrile seizure after their follow-up, and to determine the risk of febrile seizures in those with low Ig levels. Material and Methods: Between 2010-2018 a total of 320 children who had febrile seizure for the first time were admitted to the emergency department. A total of 174 children were included in the study according to the number of infections they had per year. Ig levels were compared with 189 healthy children. After 24 months, the Ig values were repeated in all children. Results: Of the 174 children, 53 (30.4%) patients had Ig deficiency (36 children with IgG deficiency and 17 children with IgA deficiency). After two years of follow-up, Ig deficiency requiring follow-up was detected in 16.7% (temporary hypogamaglobulinemia in 5.5% of infants and selective IgA deficiency in 11.2%). Of the children with Ig deficiency followed up after two years, 55.5% had complicated febrile seizure. At the end of the second year, 7.5% of the children had a diagnosis of selective IgA deficiency. The risk of complicated febrile seizure was 1.961 times higher in those with IgA<14.55 mg/dl. Conclusion: The Ig levels of children who have febrile seizure for the first time should be examined at the time of admission according to the number of infections they have experienced in a year. Although long-term follow-up is required, clinicians should be aware that IgA deficiency may be present especially in the first complicated febrile seizure.