Background: Interleukin (IL)-23 has an important role in tumor immune regulation. Objective: To investigate the possible association of interleukin-23 receptor (IL23R) gene variants rs1884444, rs10889677 and rs11209026 with development of acute lymphoblastic leukemia (ALL). Methods: The IL23R variants were studied in 164 ALL patients and compared to 175 healthy controls by polymerase chain reaction-restriction fragment length polymorphism. The relationship between these variants and clinical and laboratory features of the patients and response to therapy were evaluated. Results: No significant differences in genotype and allele frequencies existed between patients and controls. The rs1884444TG genotype was significantly lower in patients who relapsed (24.2%) compared to those without relapse (55.9%, p=0.006). Fewer patients who relapsed had evidence of the G allele (P=0.034). The TG genotype was associated with a longer complete remission at1804±116 days compared to other genotypes (<1217 days, p=0.028), however this result was not significant in multivariate analysis. The rs10889677 AA genotype and A allele was associated with age (p<0.041) and platelet number (p=0.03) in precursor-B cell ALL (B-ALL) patients. Both occurred more frequently in patients aged 2-10 years (63.6% and 66%, respectively) and in those with platelets >100×103μL (68.4% and 52.4%, respectively). Conclusion: Our findings showed a lack of association of the studied polymorphisms with the risk of ALL. The influence of the rs1884444 polymorphism on relapse rate and association of rs10889677 AA genotype with favorable prognostic factors suggest the influence of the studied polymorphisms on ALL response to therapy and prognosis.