Background: Children of parents with bipolar disorder appear to have an increased risk of early-onset Bipolar Disorder (BP), mood disorders and other psychiatric disorders. Objectives: The aim of this study was to compare the mental health of school-age children of parents, with/without bipolar disorder. Materials and Methods: This case-control study included one hundred children aged six to twelve years, who had parents with bipolar disorder and 200 children of 163 demographically-matched control parents. Parents with bipolar disorder were recruited from Farshchian Psychiatric Hospital of Hamadan, Iran, during year 2014. The parent version of the Child Symptom Inventory-4 questionnaire was used to measure mental health. Mean comparisons were performed using Student's t test while effect sizes were estimated by Cohen's d coefficient. The Chi-square test was used to assess significant differences between frequency distribution of demographic variables in both groups. The significance level was considered less than 0.05. Results: There were statistically significant differences between children of parents with and those without bipolar disorder regarding attention deficit hyperactivity disorder, oppositional defiant disorder, conduct, generalized anxiety disorder, schizophrenia, major depression, separation anxiety (P< 0.001) and social phobia (P < 0.05). Children of parents with BP are at high risk for psychiatric disorders. Conclusions: These findings support that the careful evaluation and prospective following of the psychopathology of children of parents with bipolar disorder are critical for early identification and treatment.