Objectives: In the search for new biomarkers in the diagnosis of complicated appendicitis in children, this meta-analysis aimed to investigate all available data on hyponatremia as a marker of complicated appendicitis in the pediatric population, and compare the levels of sodium in patients with non-complicated appendicitis. Materials and Methods: A total of 4 databases were searched for relevant articles, using the the search keywords (hyponatremia) AND (appendicitis) AND (children). All children with complicated acute appendicitis were eligible by inclusion criteria. The sodium levels in a group of patients with perforated appendicitis and a control group of patients with non-complicated acute appendicitis were obtained and compared. The Downs and Black scale was utilized to assess for methodological quality assessment. Results: A total of seven studies were included in this meta-analysis, of which five studies were of retrospective study design and the remaining two were prospective studies. In total, 1615 subjects had complicated appendicitis and were allocated to group A, while 2808 subjects had non-complicated acute appendicitis and were allocated to group B. The goal was to compare sodium level among the two groups. Pooling the data from the included studies revealed significantly lower serum sodium levels in the pediatric patients with complicated appendicitis compared to the patients with non-complicated appendicitis (WMD: -3.29, 95% CI=-4.52 to - 2.07, P<0.00001). The estimated heterogeneity among the included research was statistically significant and substantial (I2 =98%, P<0.00001). Conclusion: The results of this meta-analysis demonstrate that serum sodium levels are significantly lower in children with complicated appendicitis, in comparison to children in the control group with non-complicated appendicitis. It has a potential role as a biochemical marker in the diagnosis of complicated acute appendicitis.