Introduction: Breastfeeding is essential for the proper growth and development of children due to its energy and nutritional composition, immunological factors, and safety from a hygienic and health perspective. Objective: In light of this, this study aimed to assess the maternal sociodemographic factors associated with exclusive breastfeeding. Materials and Methods: A cross-sectional study was conducted with 143 pairs of mother-child less 24 months of age that were assisted in four Primary Healthcare Centers in São Luís (MA). The first form was used to collect socioeconomic and demographic data from mother-child pairs. The second form was answered by 75 mothers with early cessation of exclusive breastfeeding. The duration of exclusive breastfeeding, antenatal and postpartum care for women, social support in breastfeeding and the influence of the use of pacifiers and bottles on the cessation of exclusive breastfeeding were assessed. Fisher's Exact Test was used to check the association between the variables. Results: It was observed that 33.3% of children had exclusive breastfeeding for the first six months and that breastfeeding time was longer (93.3%) among those children who benefited from social programs. Discussion and Conclusions: The low frequency of exclusive breastfeeding time in children revealed the need to develop strategies to encourage breastfeeding in primary healthcare so that it can contribute to the qualification of nutritional and prenatal care. Como citar este artigo: Barbosa KIP, Conceição SIO. Fatores sociodemográficos maternos associados ao aleitamento materno exclusivo. Rev Cuid. 2020; 11(1): e811. http://dx.doi.org/10.15649/cuidarte.811