Purpose: to identify the knowledge of community health workers on practices and promotion of breastfeeding. Methods: this is a cross-sectional descriptive study aimed to investigate a sample of 148 health workers quantitatively and qualitatively. Data collection was performed by applying a semi-structured questionnaire with open and closed questions. The following variables were analysed: sociodemographic data, capacity to provide breastfeeding guidance, participation in training and courses, and knowledge of the breastfeeding benefits for mother and baby. Statistical analysis was performed with chi-square test, exact Fisher's test and G-test at significance level of 5%. Open questions were analysed according to the qualitative research technique.Results: approximately, 45.95% of the health workers were not trained to provide nursing mothers with practical guidance on breastfeeding, and 63.30% never attended courses on breastfeeding. The majority of health workers mentioned breastfeeding benefits only for the baby, namely: nutrition, immunology, development, health, dentition, and bones. There was a statistically significant association between the capacity to provide breastfeeding guidance and participation in training (p<0.001). Conclusion: the health workers had not participated in training courses to follow up nursing mothers, in addition to having a limited knowledge on practices and promotion of breastfeeding and paying late postnatal home visits.