Objective: To evaluate the effect of using an educational booklet combined with a brief motivational interview on maternal self-efficacy in preventing childhood diarrhea. Methods: Quasi-experimental study, carried out with 35 mothers. For data collection, the Maternal Self-Efficacy Scale for the Prevention of Childhood Diarrhea (EAPDI) was applied, and later an educational intervention based on the application of the booklet “You are able to prevent diarrhea in your child!” associated with a brief motivational interview. One month after the intervention, by telephone contact, the EAPDI and a form to verify the occurrence of diarrhea were applied. For data analysis, statistical tests were applied. The study was approved by the Research Ethics Committee. Results:Houve aumento dos escores de autoeficácia materna em prevenir a diarreia infantil ao longo do estudo (p 0,001), aumento progressivo do número de mães que apresentaram alta autoeficácia (p 0,001) e diminuição da ocorrência de casos de diarreia um mês após a intervenção (p 0,021). Conclusões: A intervenção educativa ajudou a aumentar a autoeficácia materna na prevenção da diarreia infantil e na redução dos episódios de diarreia nas crianças, revelando-se também um instrumento capaz de aumentar a autonomia das mães no cuidado das crianças.