Tonsils are one of the most significant secondary lymphoid organs in immune system. They contain B and T lymphocytes. B cells produce all five classes of immunoglobulins. The tonsillectomy's effect on the immune system is still up for debate. Objective: The study was done to observe the effect of tonsillectomy on humoral immunity parameters (IgA, IgM, and IgG) in children with obstructive sleep apnea before and after tonsillectomy. Patients and methods: A total of 60 patients who were scheduled for tonsillectomy because of obstructive sleep apnea, with ages below 3 years, and diagnosed by clinical findings of adenotonsillar hypertrophy by otorhinolaryngology surgeons were included. Serum levels of immunoglobulins (IgA, IgG, and IgM) were measured in all patients before tonsillectomy after 1 and 3 months of the operation. Results: There was a decrease in IgG levels 1 month after surgery (P ¼ 0.005) but they were still within the normal range. At 3 months of follow-up, there were no significant differences between the postoperative and preoperative levels (P ¼ 0.16). At 1 month and at 3 months of follow-up, IgA and IgM serum levels were considerably lower than their levels before the operation (P < 0.001), although they were still within the normal range. Conclusions: After tonsillectomy, humoral parameters (IgA and IgM) were found to be reduced, but there was no effect on immune status. IgG level was not affected after 3 months of tonsillectomy.