Aim: To evaluate the reliability of different RBC indices to differentiate between Beta thalassemia trait and iron deficiency anemia in children. Materials and Methods: The present prospectivestudy was conducted in Department of Paediatrics, Mahatma Gandhi Medical College & Hospital, Jaipur from March 2021 to July 2022 among 105 patients admitted in Department of Paediatrics for anemia. Erythrocyte microcytosis and hypochromia was assessed using automated blood cell counter and by peripheral smear. All cases with normal MCV and MCH will not be tested further. The cases with reduced level of serum ferritin were labelled as IDA while those with normal or increased serum ferritin level were subjected to HPLC examination. 10 indices were calculated among both groups using CBC parameters. Sensitivity and specificity, PPV, NPV, DA &Youden’s index for these indices were calculated.Results: 91 (86.67%) subjects had Iron Deficiency Anemia and 14 (13.33%) patients were of Thalassemia. RDW, Mentzer index and Kerman 1 index gave the correct diagnosis in 97.14%, 95.24% and 95.23% of the patients respectively. Rest all the indexes gave accuracy of >80% except SHINE AND LAL INDEX which gave accuracy of only 19.05%. None of the indices studied showed 100% sensitivity or specificity. However, SLIMCVXMCVXMCH/100 index demonstrated highest sensitivity (98.3%) to detect β thalassemia trait but low specificity (8.4%). RDW index showed second highest sensitivity (84.9%) followed by MENTZERS (MCV/RBC). Conclusion: Result of present research leads to conclusion that the percentage of correctly diagnosed patients was highest with RDW followed by Mentzer index, RDW and Kerman 1 index. The results of the current study highlight the fact that red cell indices are now reasonably sensitive, specific, reproducible, and exact and can be relied upon for usage in peripheral health clinics without access to more expensive tests like electrophoresis and HPLC. Additionally, it can reduce the costs associated with β-Thalassemia mass screening.