Background and purpose: The prevalence of behavioral problems in children with mentally ill parents may be higher compared to children with mentally healthy parents. This study was carried out to assess the behavioral problems in children with bipolar mothers. Material and methods: This case-control study was conducted between 50 children (6-11 years) of mothers with bipolar I disorder as a case group and 50 children of healthy mothers as control group in Sari, Iran, during 2011-13. With psychiatric interview based on DSM-IV-R and Minnesota Multiphasic Personality Inventory (MMPI), bipolar disorder in mothers was confirmed and other prominent psychiatric disorders were ruled out. The psychological health of control mothers was confirmed using psychiatric interview and general health questionnaire (GHQ). The behavioral problems of children in two groups were compared using Achenbach child behavior questionnaire. Data were analyzed using SPSS-19, Chi- Square and Student’s t-test. Results: Somatic complaints, anxiety and depression, social problems, externalization and internalization scores and also behavioral problems total scores were significantly higher in case group compared to control group (P< 0.05). No significant differences between case group and control group were mentioned with respect to isolation, attention problems, thought problems, antisocial behaviors. Conclusion: Psychiatric and behavioral problems in children with bipolar mothers were higher, compared to children of healthy mothers. Child psychological counseling and psychiatric management in along to mothers’ treatment is advisable.