Familial Mediterranean fever (FMF) is the most common inherited periodic fever syndrome characterized by recurrent episodes of serositis. Recently, a few studies have suggested that FMF is related to increased risk of atherosclerosis. Mean platelet volume (MPV) is a marker of platelet activation. Larger platelets are associated with increased atherosclerosis risk. The aim of the study is to evaluate levels of MPV in pediatric FMF patients during and between attacks. The study consisted of 48 patients during an attack (group 1), 63 patients in attack-free period (at least 2 weeks after an attack, group 2), and 49 healthy controls (group 3). Erythrocyte sedimentation rate, C-reactive protein, white blood cell count, platelet count (PLT), and MPV levels were retrospectively recorded from the computerized patient database. Mean platelet volume was significantly lower in FMF patients during attack than in attack-free period (p = 0.00); however, there was no difference among attack-free patients and healthy controls (p = 0.38). The mean platelet counts of FMF patients during attack were higher than the healthy controls (p = 0.02). There was an inverse correlation between MPV and mean PLT in the attack-free period (r = -446, p = 0.01). This study suggests that an early atherosclerosis marker, MPV, is not elevated in pediatric FMF patients on colchicine treatment.