Background: Necrotizing Fasciitis is a rapidly progressive soft tissue infection that is life and limb threatening without prompt treatment. LRINEC score is the most commonly used scoring system for its diagnosis. This study aims to compare SIARI score with LRINEC score for diagnosis of NF. Method: This was a prospective, comparative observational study of 42 patients admitted in Bir Hospital with provisional diagnosis of necrotizing fasciitis between August 2020 and March 2021. SIARI score and LRINEC score at admission were calculated and compared to final diagnosis on the basis of histopathology reports and with regards to sensitivity, specificity, positive predictive value, negative predictive value and C-statistic. Results: Out of enrolled 42 patients, 32 had final diagnosis of NF. The mean age was 46.59 ± 15.58 years with male to female ratio being 2.2:1. The most commonly affected site was lower limb (59.4%) and polymicrobial infections (59.4%) were common. Trauma (40.6%) was the most common risk factor. The most common co-morbid conditions were chronic alcoholism (65.6%) and diabetes mellitus (34.4%). Mortality rate of 15.6% was noted. Sensitivity, specificity, PPV, NPV and C-statistic of SIARI score ? 3 and LRINEC score of ? 6 were 78.1% vs. 62.5%, 70% vs. 60%, 89.3% vs. 83.3%, 50% vs. 33.3% and 0.827 ( p < 0.001) vs. 0.650 (p < 0.0962) respectively. Conclusion: SIARI score is an easy to use tool for diagnosis of Necrotizing Fasciitis exhibiting better sensitivity, specificity and diagnostic accuracy compared to LRINEC score.