Background: A sedentary lifestyle is associated with higher mortality and the development of chronic pathologies. In children and adolescents, sedentary behavior for more than 2 h/day is associated with unfavorable body composition and physical condition, and lower levels of self-esteem, sociability and school level. However, more than 50% of children (6-10 years) spend on average more than 3 h/day in front of a screen, and this time continues to increase (+20 min from 2007 to 2015) [1]. In this context, designing and testing effective interventions to decrease sedentary behavior in children is a major public health research gap. Objective: The CIPRES intervention is co-constructed with key local actors, multilevel with a socio-ecological approach [2], and theory-based on the transcontextual model [3]. The CIPRES intervention aims to reduce sedentary time in school-age children (7-10 years). A secondary aim is to evaluate the effect of the CIPRES intervention on sedentary according to social deprivation level. Methods: The intervention will be evaluated by a cluster-randomized and controlled study. The target population will be made up of 1000 children in CE2-CM1 from primary schools in 4 towns in Toulon area with different levels of social deprivation. The study involves 2 phases: (1) Co-construction of an intervention for sedentary prevention adapted to the local context by using a participatory approach including representatives of each "level" of actor (i.e., children, teachers, parents, associative and municipal staff, educational advisers). (2) Implementation of the intervention in the local context [4]: the intervention lasts 6 weeks and aims to reduce sedentary behavior at different times in the child's life: school, after-school and family times. The effects of the intervention will be assessed before (T0), after the intervention (T1) and 6 months after the end of the intervention (T2). Main outcomes include sedentary behavior, level of physical activity, sleep, and variables of the transcontextual model (i.e., motivation, attitudes, norms, perceived control, intentions), and will be measured by accelerometry, diary or questionnaires. Results/discussion: A pilot intervention was co-constructed and a feasibility study is currently underway. This feasibility study involves around 90 children from primary schools. The first results on the feasibility of the implementation and the pre- vs post-intervention effects on children's sedentary time and variables of the transcontextual model will be available by summer 2021. Conclusion: The CIPRES study will assess a multilevel intervention aiming at reducing sedentary behavior in school-aged children. The intervention is based on the socio-ecological perspective and relies on a participatory design, in line with recent concerns regarding complex public health programs, social inequalities and the need to combine both agentic and structural strategies in such interventions.