Background: In this study, the clinical and laboratory findings, complications, and responses to regular intravenous immunoglobulin (IVIG) treatment of 34 patients diagnosed with primary immunodeficiency (PID) carrying transmembrane activator and CAML interactor (TACI) protein mutations were retrospectively evaluated. Material and Method: Clinical characteristics of patients, complete blood counts, serum immunoglobulin and compleman levels, lymphocyte subgroups, and mutation types of the patients followed up in our clinic for PID and diagnosed with TACI Mutation with Next Generation Sequencing (NGS) Method were examined. Results: A total of 20 (59%) of the patients were male, 14 (41%) were female, 18 were children (<18 years old) who had a median age of genetic diagnosis of 6.2 years and 16 were adults (>18 years) with a median age of genetic diagnosis of 34 years. The most common complaint was recurrent respiratory tract infection (68%). According to the Euro Class Classification (ECC), 14 patients who met the diagnostic criteria of Common Variable Immunodeficiency (CVID) had significantly lower lymphocyte, naïve (CD19+IgD+27-), non-switched (CD19+IgD-27+) number and percentage of B cells than the 20 patients who did not match (p<0.05). A total of 24 of the 34 patients, 13 of whom were children and 11 of whom were adults, received regular IVIG treatment because they met the criteria for ECS and/or had comorbidities. Conclusion: In our study, the fact that bronchiectasis and recurrent pneumonia and the need for hospitalized treatment were less common than in the literature was thought to be related to early IVIG treatment.