This study was conducted with a study group consisting of parents to define the relationship between obesity and the family environment related to nutrition and physical activity in school-aged children aged 5–14 years and to determine the relationship with the variables of school level, gender, and parental education level affecting this environment. The study was conducted online with 531 parents—289 male (father) and 242 female (mother)—who have children in preschool, primary, and secondary school during the fall semester of 2024. Data were collected with questions designed to determine sociodemographic characteristics, and the Family Nutrition and Physical Activity Screening Scale (FNPA-TR) was adapted into Turkish. The relationships between the scores obtained from the FNPA scale and children's body mass index (BMI), as well as some socio-demographic variables, were examined using the appropriate variance model and correlation analysis according to the structure and distribution of the data. When examining the results of this study, it was revealed that the higher education level of parents contributes to children having lower BMI values. In addition, it was observed that family and child activities play an important role in children's BMI, and children with lower BMI were more active. A healthy environment and family sleep patterns were also found to positively affect BMI. The gender of the children did not make a significant difference in BMI. It is clear that family dietary habits and physical activity levels are important factors influencing childhood obesity risk, but family eating patterns and dietary habits do not directly influence BMI in interaction with environmental factors.