Purpose: We aimed to measure peripapillary retinal nerve fiber layer (RNFL) thickness in children with thalassemia major (tha-major), children with iron deficiency anemia (IDA), and children in a healthy control group. Materials and Methods: A total of 47 children with tha-major and 22 children with IDA were selected from two pediatric hematology outpatient clinics as our experimental groups, while 35 healthy children were randomly selected from a primary school to act as a control group. After a complete eye examination was conducted and intraocular pressure measurements were obtained, RNFL measurements were performed using optical coherence tomography, and the information was recorded for statistical analysis. Results: The mean age of the participants was 9.65 +/- 4.13 years in the tha-major group, 9.14 +/- 2.53 years in the IDA group, and 9.13 +/- 3.29 years in the control group, respectively, with no statistically significant difference among the three groups (p>0.05). Mean peripapillary RNFL thickness was 119.38 +/- 35.49 microns in the tha-major group, 184.00 +/- 31.14 microns in the IDA group, and 187.73 +/- 27.36 microns in the control group. It was significantly thinner in all quadrants in the tha-major group vs. the other two groups (p<0.01), and in only the inferior quadrant in the IDA group (p<0.05). Average RNLF thickness correlated positively with mean hemoglobin value (r = 0.488; p<0.001) and negatively with mean ferritin level (r = -0.544; p<0.001), but no correlations with mean number of transfusions and mean visual acuity were observed (p>0.05). Conclusion: The study revealed that peripapillary RNFL is thinner in tha-major in all quadrants and in only the inferior quadrant in IDA. Thinning of the RNLF correlated with hemoglobin value and ferritin level, but not with number of transfusions and visual acuity.