Parental behaviors and attitudes are effective in health outcomes of children. Obesity among children has been found to be related with limited nutrition knowledge and unhealthy eating and habits. Therefore, this study identified the causes and factors associated with obesity among children and revealed their own routines from the perspective of mothers. Content analysis was used in the current qualitative research. Potential and eligible participants were selected by visiting four preschool centers in Sarab, Iran. The height and weight of 113 children aged 5-6 years were measured by standard scales, along with calculating their body mass index. The mothers of children at or above the 50th percentile were invited to appointments for interviews in the preschool centers. Then, 37 semi-structured face-to-face interviews were carried out with mothers and analyzed by two independent researchers manually. The factors associated with obesity in preschool children were categorized into four main themes, including insufficient physical activity, poor perception of body weight, unhealthy behavioral habits, and genetic factors. The mothers did not consider their children at risk of becoming overweight, as their perceived sensitivity was low. The results of this study can be supportive in designing family and parent-centered interventions to control obesity among children.