No study to date has simultaneously tested how poor peer relations, generic risk factors, and parental attitudes impact the behavioral and emotional challenges of children who vary in their gender expression. In a community sample, the present study investigated various hypothesized psychosocial and generic risk factors regarding the association between childhood gender nonconformity (GNC) and psychological well-being. Canadian parents/guardians reported on their children aged 6–12 years (N = 1719, 48.8% assigned male at birth) regarding their child’s GNC, measured by the Gender Identity Questionnaire for Children; behavioral and emotional challenges, measured by the Child Behavior Checklist (CBCL); and peer relations, measured by the CBCL and Strength and Difficulties Questionnaire. Parent/guardian gender-stereotypical attitudes toward child-rearing were assessed using an adapted version of the Child-Rearing Sex Role Attitude Scale, and attachment between the parent/guardian and child was measured with an adapted version of the Child-Rearing Practices Report. Based on regression analyses, GNC was related to elevated behavioral and emotional challenges, and this association was stronger for those who experienced poor peer relations as well as for those whose parents/guardians endorsed gender-stereotyped attitudes and were less willing to serve as a secure base for the child. Recommendations are provided for ways in which social environments can be altered to improve psychological well-being among gender-nonconforming children.