The purpose of this study was to understand the effects of pediatric bipolar disorder on child siblings. A quantitative quasi-experimental research design was used. According to family systems theory, which was used in the formation of this study, all family members are interconnected and affect each other in a variety of ways. The research questions investigated whether children demonstrated more emotional dysregulation and fewer adaptive skills when a bipolar sibling was living in the home than when there was no bipolar sibling. The matched comparison study used 2 groups of children: those with bipolar siblings and those without bipolar siblings. Parents completed the BASC-2 Parent Rating Scale in order to measure adaptive skills and emotional dysregulation in their non-bipolar children. Parents were recruited via social media parent support sites. Thirty-four families included in the study group had 1 bipolar child and at least 1 nonbipolar child living in the home; 31 families in the comparison group had no bipolar children. All children were under the age of 18, living together full time, had a biological or legal relationship, and did not have any other mental health diagnosis. A multivariate analysis of variance was used to test the hypotheses. The study found that children with bipolar siblings demonstrated significantly higher levels of emotional dysregulation (both externalization and internalization) than did children without bipolar siblings. There was no significant difference in reported adaptive skills between the 2 groups of children. This study has social change implications as it identifies the emotional needs of sibling children who are routinely overlooked as needing assistance. This study provides the groundwork for clinicians and educators working in the pediatric mental health field to begin exploring potential treatments and programs for siblings of bipolar children.