Immunoglobulin A (IgA) deficiency is the most common primary immunodeficiency in humans, with incidence depending on ethnic background and the highest frequency in Caucasians. Selective IgA deficiency may have an asymptomatic course and constitute a random laboratory finding with no clinical manifestation. There is, however, a group of patients with increased incidence of recurrent upper respiratory tract infections, allergies, asthma, atopic dermatitis and other pathologies connected with IgA deficiency. This group of patients often needs broad-spectrum antibiotic therapy with maximum doses and extended time of treatment as there is no causal treatment for IgA deficiency. An association between IgA deficiency and autoimmune diseases, such as juvenile idiopathic arthritis, has been proved before. Nonetheless, the frequency of co-occurrence of these disorders in an individual as well as the way immunodeficiency may influence the course of juvenile idiopathic arthritis is still undefined, with limited literature on this topic. This article presents case reports of three pediatric patients with confirmed co-occurrence of IgA deficiency and oligoarticular juvenile idiopathic arthritis.