This study explored parents' and preschool personnel's opinions on factors influencing 3-5-year-old children's sedentary behaviors by applying the socioecological model. Four focus group interviews with preschool personnel (N = 14) and six interviews with parents (N = 17) were conducted in autumn 2014. Two researchers independently analyzed the data. A key finding was that the factors influencing children's sedentary behaviors were recognized at all levels of the socioecological model. Parents and personnel acknowledged that children's age, gender, and personal characteristics had an influence on the incidence of sedentary behaviors. The physical and social environments at home and at preschool seemed to work in a synergetic way. Sedentary behavior was focused on screens at home because of the wide variety of screens available for children to use. On the other hand, the existence and use of screens in preschools were rare. The routines and structures of the daily agenda in preschool define the sedentary behaviors, and how much children sit is dependent on personnel's motivation. Hurriedness and lack of rules at home increased children's sedentary behaviors. Overall, the vast majority of the preschool personnel and parents shared an understanding that the children in their care were not sedentary. The findings of this study support the use of the socioecological model in shedding light on the sedentary behaviors of preschool children. Interventions targeted at diminishing preschool children's sedentary behaviors should focus on different aspects of sedentary behaviors at home and at preschool.