Background: This study addressed differences between parent–child dyads with excessive body mass (overweight or obesity) and dyads with normal body mass in obesity determinants, derived from social-ecological models. It was hypothesized that parents and their 5–11 years-old children with excessive body mass would (1) report lower availability of healthy food at home, (2) perceive fewer school/local community healthy eating promotion programs, (3) report lower persuasive value of food advertising. Methods: Data were collected twice (T1, baseline; T2, 10-month follow-up), including n = 129 parent–child dyads with excessive body mass and n = 377 parent–child dyads with normal body mass. Self-reported data were collected from parents and children; with body weight and height assessed objectively. General linear models (including analysis of variance with repeated measures) were performed to test the hypotheses. Results: Compared to dyads with normal body mass, dyads of parents and children with excessive body mass perceived lower availability of healthy food at home and fewer healthy eating promotion programs at school/local community (T1 and T2). These effects remained significant after controlling for sociodemographic variables. No significant differences in persuasive value of food advertising were found. Conclusions: Perceptions of availability of healthy food at home and healthy nutrition promotion may be relatively low in parent–child dyads with excessive weight which, in turn, may constitute a risk factor for maintenance of obesity.