Hepatitis A virus (HAV) still continues to be a serious public health problem worldwide. Mean platelet volume (MPV) is a marker of platelet function and activation. This study aimed to evaluate the relationship between MPV in acute hepatitis A patients as compared to the control group and to assess MPV as an acute phase reactant in acute hepatitis A.Seventy-six patients were enrolled in this study. The control group consisted of 41 healthy age- and sex-matched individuals. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, prothrombin time (PT), platelet count (PC), serum albumin (ALB), and mean platelet volume (MPV) levels were recorded. The diagnosis of HAV infection was based on anti-HAV Ig M positivity.The mean levels of MPV in the study group were significantly statistically lower than in the control group (p 0.05), but the MPV levels correlated with the platelet counts (p < 0.05). A 9.75 fL [area under the curve (AUC: 0.756)] optimal cutoff level of MPV with a sensitivity of 69.7% and specificity of 68.3% was determined in the children with acute hepatitis A.MPV levels were significantly lower in the patients with acute hepatitis A as compared to the healthy control group. This study demonstrated that MPV may be a negative acute phase reactant for acute hepatitis A. Further studies will explain the role that MPV plays in inflammation and other viral infections.