Background and Objective: The Happy Child Program (Programa Criança Feliz - PCF, in Portuguese) reaches 1.4 million Brazilian children under three years of age with home visits aimed at promoting neuropsicomotor development. Based on a conceptual model, PCF implementation and impact were evaluated in a randomized study in 30 municipalities. Thus, we aim to present the Results of this impact evaluation of the PCF program. Methods: A total of 3242 children were allocated to the intervention (IG) or control (CG) group, 80.0% of whom were prospectively followed up from late 2018 to late 2021. Development was assessed by the Ages and Stages Questionnaire (ASQ3). During the three-year study period, visits were replaced by virtual contacts for an average of 12 months due to COVID-19. At the endline survey, intent-to-treat analyses showed mean scores of 203.3 in the IG and 201.3 in the CG. Additional analyses using instrumental variables and propensity scores matching also showed no effect, since the number of contacts with the program was not associated with ASQ3 scores. Results: No impact was observed on stimulation, responsive interactions, or psychological attributes of children. The implementation study revealed low coverage in the IG, contamination of the CG, deficiencies in management and low quality of visits in many municipalities. Conclusions: The study did not demonstrate an impact of PCF implemented under routine conditions but provides elements for its improvement. Additionally, these results show that several measures are needed to strengthen the implementation of the program, so that the stakeholders can ensure investment in early childhood as one of the priorities.