BACKGROUND: Mean platelet volume (MPV), which is commonly used as a measure of platelet size, indicates the rate of platelet production and platelet activation. We aimed to evaluate the mean platelet volume in children with hepatitis A. METHODS: In this retrospective case-controlled study, the study population consisted of 62 children with hepatitis A and 62 healthy control subjects. RESULTS: MPV values, aspartate transaminase (AST), and alanine transaminase (ALT) levels on admission were significantly increased in patients with hepatitis A when compared to controls whereas white blood cell (WBC) counts were significantly lower. Two weeks after admission, the MPV values showed a significant decrease from 9.47 ± 1.62 to 8.84 ± 1.48 fL in patients with hepatitis A, but these values were still significantly higher than the controls. There was a significant difference in terms of MPV, WBC, AST, and ALT values between the controls and the patient group 2 weeks after admission. CONCLUSIONS: This study is the first to evaluate the MPV levels in children with hepatitis A. MPV values were found to be increased in children hospitalized with hepatitis A.