Background/aims: Crohn's disease frequency has increased in recent years in Iran. Genetic and environmental factors predispose people to this disease. Mutation in Caspase Recruitment Domain 15 (CARD15) gene is the most well known genetic predisposing factor to this disease. Frequency of three common CARD15 mutations has been studied in different ethnic groups. We aimed to study the frequency of these mutations in Iranian patients affected with Crohn's Disease.Methodology: One hundred fifteen proved cases of Crohn Disease and 115 age and sex matched normal controls were recruited in this study. Lf1007fs, R702W and G908R mutations were studied by Polymerase Chain Reaction-Restriction Fragment Length Polymorphims (PCR-RFLP) followed by sequencing the positive cases.Results: Lf1007fs and G908R mutations were not found in either patients or age-sex matched controls. Just in two patients, R702W mutation was proved by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) and sequencing. None of these patients had illeal or fibrostenotic type of disease while 14.7% of total patients had stricturing type of disease. No complication was seen in these two patients while 50.4% of patients had acquired complications during the course of disease.Conclusion: The three mutations described are not responsible for the pathogenesis of Crohn's Disease in Iranians. The results are in accordance with other Asian nations' studies on IBD Patients.