Intellectual disability is associated with increased risk for childhood obesity, and the factors most often associated with this risk are incorrect eating behavior and insufficient amount and intensity of physical activity. As is well known, there area whole range of factors determining lifestyle, but many currently available reports in this field refer to the functioning of children without a diagnosis of intellectual disability, and, as we know, due to numerous individual and environmental barriers, children with ID may function differently in this context than their peers. Therefore, we examined the relationships between the selected variables and divided them into two models: (1) first regression model: child’s willingness to engage in physical activity (dependent variable), child’s physical limitations related to disabilities and/or comorbidities, child’s independence, parents’ willingness to engage in physical activity, child’s body dissatisfaction (independent variables/predictors); (2) second regression model: child’s emotional eating (dependent variable), child’s coping with emotions, parents’ attitudes, beliefs, and practices about child feeding (restriction and pressure to eat), parents’ emotional eating, parents’ happiness (independent variables/predictors). A group of 503 parents (of children and adolescents with mild and moderate intellectual disability) completed: the Contour Drawing Rating Scale, the Child Feeding Questionnaire, the Emotional Overeating Questionnaire, the Scale of Experiencing Happiness, and the supplementary survey. Our results allow partial confirmation of the hypotheses related to both of these models: (1) model I: the relationships between the child’s willingness to engage in physical activity and all predictors are significant, but the direction of the relationship between the dependent variable and one of the predictors—body dissatisfaction—is opposite to the assumed one (negative relationship); (2) model II: the relationships between the child’s emotional eating and almost all predictors are significant, except for the relationship between the dependent variable and pressure to eat. In conclusion, (to the authors’ knowledge) this study is the first to assess dyadic predictors of willingness to engage in physical activity and emotional eating in children and adolescents with mild and moderate intellectual disability. It allows for a better understanding of the attitudes, beliefs, and experiences of children with intellectual disabilities and their parents, which gives the opportunity (taking into account factors from both individuals from the child-parent dyad) to better design strategies to support pro-health behaviors in children and adolescents from this group (which may improve the effectiveness of overweight prevention and obesity). These findings emphasize how important it is to consider the dynamic of the child-parent dyad when considering how parenting contributes to a child’s willingness to engage in physical activity, as well as thatchild’s emotional eating.