Background: The aim of this study was to analyze the knowledge and practices of dentists regarding breastfeeding as a strategy for promoting children's oral health. It also aimed to investigate how nursing mothers perceive the participation of dentists in actions to promote and support breastfeeding. Methods: this study employed a mixed methodological approach. During the quantitative phase, 91 dentists of the Family Health Strategy answered an electronic questionnaire, and the data were analyzed using descriptive statistics. For the qualitative investigation, were interviewed 21 nursing mothers. These interviews were examined through content analysis, and the results were interpreted from the perspective of the Theory of Planned Behavior. Results: Among dentists, 81.3% agreed that they are aware of the implications of breastfeeding for the child's oral health and reported 72.8% advising mothers and pregnant women about its benefits. Ambivalent social norms and weaknesses related to actions promoting and supporting breastfeeding emerged in the speeches of nursing mothers, and unfamiliarity about the benefits of this practice for children's oral health. Conclusions: Dentists recognize the benefits of breastfeeding for children's oral health. On the other hand, the nursing mothers pointed out barriers, exposed weaknesses, and signaled necessary conjunction of efforts to improve maternal and child care quality.