OBJECTIVES: The aims of this study were to examine factors related to 1) parental perception of health risks for overweight children and 2) parents' self-efficacy for influencing their children's dietary and physical activity behaviors, especially in relation to family history (FH) of diabetes and cardiovascular disease (CVD). METHODS: A consecutive sample of parents was surveyed at 7 primary care practices about FH, perceptions of childhood obesity-related health risks, health beliefs, and perceptions. Generalized estimated equation models clustering on practice were developed to examine associations with perceptions and self-efficacy. RESULTS: Analyses included 386 parents of children aged 2 to 17 years. Sixty-seven percent had FH of CVD and 33% had FH of diabetes. Children were 57% white, 23% Hispanic, 12% African American, and 8% other race/ethnicity; 17% were overweight and 18% were obese. Parents whose child had FH of diabetes more often perceived higher risk of diabetes for overweight children than those with neither FH risk (adjusted odds ratio [OR] 1.4, 95% confidence interval [95% CI], 1.2-1.7), as did those with FH of CVD (adjusted OR 2.0, 95% CI, 1.6-2.5) and those with an obese child. Parents with less than college education or having African American and female children perceived risk less often. Parents had high self-efficacy for influencing their child if they had a strong belief in parental modeling and their child was aged <12 years. CONCLUSIONS: Family history of diabetes and CVD and other factors are associated with parents' perceptions of health risks for overweight children. Strategies to use FH to motivate families with overweight children toward behavior change are needed.