Introduction: Fluid intake was reported to reduce migraine attacks. This may be due to its effect on hemoconcentration. Hemoconcentration may manifest itself by increasing in the hemoglobin and platelet-related values. This study aimed to reveal hemoconcentration by evaluating complete blood cell counts in attack-free periods of pediatric patients with migraine. Materials and Methods: Consecutive children with migraine (n = 70) and tension-type headache (TTH) (n = 65) were compared with the control groups. Control 1 (n = 70) and control 2 (n = 60) groups consisted of age- and gender-matched patients, respectively. Control 2 group patients had gastrointestinal symptoms leading to fluid loss, which may have caused hemoconcentration. To evaluate hemoglobin and platelets together, the M1-value was created by multiplying hemoglobin level by plateletcrit. Results: The M1-value was higher in the migraine group than in control 1 and TTH groups (P = 0.017 and 0.034) and the hemoglobin and hematocrit levels were also higher in the migraine group than in control 2 group (P = 0.013 and 0.012). Female patients with migraine had higher hemoglobin levels as compared to the female patients in control group 1 (P = 0.041). Male patients with migraine had higher M1-values than the male patients in control group 1 (P = 0.034). In the subgroup of migraine with aura (n = 10), folic acid was significantly lower than the other patients with migraine (P = 0.02). Conclusion: This study suggests that migraine may be accompanied with hemoconcentration in children.