Background: Diabetic ketoacidosis (DKA) is the most common acute hyperglycemic emergency in children with diabetes mellitus. DKA is the consequence of an absolute or relative lack of insulin and concomitant elevation of counter-regulatory hormones, usually resulting in the triad of hyperglycemia, metabolic acidosis and ketosis. This study aimed to determine the frequency and prognostic significance of serum lactate in children with diabetic ketoacidosis admitted to the Pediatrics department. Methods: This study was a comparative cross-sectional study that included sixty participants. They were divided into 30 children with diabetic ketoacidosis and 30 age- and sex-matched healthy children as a control group. Results: There was a significant negative correlation between serum lactate and venous PH (P = 0.001). There was a significant positive correlation between serum lactate and CRP (P = 0.029). There was a significant negative correlation between serum lactate and recovery time (P = 0.016). Conclusion: Lactic acidosis is common in DKA, unlike other conditions such as sepsis, and is not always a finding that predicts the severity of the disease or mortality.