ABSTRACT: BACKGROUND:Difficulties with delaying gratification, coping with frustration, and regulating emotions are significant predictors of aggression and behavioural and interpersonal problems early in life and mental health disorders during childhood, adolescence, and adulthood. Mental health problems generate a high burden of disease in society in general, and there is a significant treatment gap, especially among economically vulnerable populations. Prevention strategies appear to be the more recommendable options, mainly if these interventions can be implemented early in life and at low cost. Few preventive interventions aiming to increase resilience in the face of adversity have been rigorously evaluated among Chilean preschoolers. Substantial international evidence indicates that strengthening basic psychological skills, such as emotion regulation and social problem-solving, can reduce the incidence of mental pathology and improve various academic indicators. The curriculum of the Interpersonal Cognitive Problem-Solving Programme, also known as I Can Problem Solve (ICPS), is focussed on the development of the cognitive process and children's social problem-solving skills. ICPS is effective at increasing prosocial behaviours and reducing aggressive behaviour among preschoolers. ICPS provides children with the skills to think about how to solve problems using sequenced games, discussion, and group-interaction techniques focussed on listening to, and observing, others, promoting empathy and alternative and consequential thinking. The aims of this study are (1) to develop a culturally appropriate version of the ICPS programme and (2) to evaluate the acceptability and feasibility of the adapted version of ICPS among vulnerable schools in Santiago, Chile, conducting a pilot randomised controlled trial with three arms: (1) the ICPS programme delivered by an internal early teacher, (2) the ICPS programme delivered by an external early teacher, and (3) a control group. METHODS AND DESIGN:This is a pilot, three-armed randomised controlled trial of the adapted version of ICPS with an enrolment target of 80 preschoolers attending four schools per arm. Children in both intervention groups will receive the ICPS programme: 59 sessions of 20?min each delivered three times a week by trained internal or external early teachers over 5-6?months. Internal teachers are part of the school staff, and external teachers are facilitators hired by the research team to go to schools and deliver the intervention during a normal school day, working together with the early teacher present in the classroom. The intervention consists of games using pictures, puppets, and simple role-playing techniques to facilitate the learning process. Cognitive regulation, emotion recognition, social-problem-solving skills, and psychological functioning will be measured at baseline and after the intervention. DISCUSSION:No previous studies in Spanish-speaking Latin American countries have been conducted to explore the acceptability and feasibility of ICPS to provide information to evaluate the effectiveness of this intervention on a larger scale. TRIAL REGISTRATION:ClinicalTrials.gov, ID: NCT03383172 . Registered on 26 December 2017.