Aims: To assess the clinical and radiographic effectiveness of NIET utilizing 0.5 mg/ml, 2.5 mg/ml and 5 mg/ml concentrations of modified triple antibiotic paste (mTAP) consisting of amoxicillin, metronidazole and ciprofloxacin, in necrotic primary molars Settings and Design: 96 non-vital primary molars in children aged 5 to 9 years were randomly allocated into three groups of different concentrations of mTAP (Group I: 0.5 mg/ml, Group II: 2.5 mg/ml and Group III: 5 mg/ml), based on MIC value of combination of antibiotics against E. faecalis. Methods and Material: Different concentrations of mTAP were prepared, using raw powders of antibiotics with propylene glycol as vehicle. After NIET, clinical follow-up was done at 1, 3, 6 and 12 months whereas radiographic evaluations were conducted at 6 & 12 months. Statistical analysis used: Chi-square test and Fisher’s exact test was used to find association between categorical variables. A value of P ≤ 0.05 was taken to be statistically significant. Results: After 12 months follow-up, 2.5 mg/ml concentration group had highest clinical and radiographic success as compared to the other two concentration groups. Conclusions: Modified triple antibiotic paste (mTAP) in concentration of 2.5 mg/ml, demonstrated good clinical and radiographic outcomes in NIET of necrotic primary teeth.