Establish the sensibility and specificity of the neutrophil-lymphocyte rate (NLR) in pediatric patients with acute complicated appendicitis.Transversal, observational, descriptive, and retrospective study of pediatric patients between 4 to 16 years old with diagnosis of acute appendicitis, who had appendectomy, from December 2017 to January 2019. We calculated the NLR in every patient. To analyze the variables, we used the test of Mann-Whitney and we value the sensibility and specificity of the NLR.There were 245 patients, 81 with simple appendicitis and 144 with complicated appendicitis. Just 27 of them were laparoscopic appendectomy. The NLR had a media of 10.48 in simple appendicitis, and 13.03 in complicated ones, with a p value of 0.02. the area under the curve was 0.622. There was a rate of 8.2 in complicated appendicitis to the NLR.The NLR has been poorly studied in pediatric patients with acute appendicitis. In this study the NLR had a significant value in the patients with acute complicated appendicitis, with medium sensibility and a relatively low specificity.