Goal: To investigate the causes that lead to early interruption of breastfeeding (BF) in users of Basic Health Units (UBS) in Santa Maria, Rio Grande do Sul. Methodology: Research with a cross-sectional, prospective design, with a quantitative approach, of a descriptive nature, with 70 mothers of children up to 2 years of age, through simple random sampling. Held at UBSs in the city of Santa Maria -RS, from October to December 2021. Statistical analysis of data using IBM SPSS Version 25 software and the EXCEL program. Descriptive data analysis, with categorical variables presented as percentages and quantitative variables as averages, and qualitative variables analyzed using the chisquare test or Fisher's exact test. Results: The most frequent complaints cited, when asked about the reasons that led to early interruption of BF, were little milk (66.7%), nipple injury (42.4%) and difficulty latching on (18.1%). 45.7% of the interviewed mothers reported early interruption of exclusive breastfeeding (EBF), before 6 months of life, and 25.7% of BF, before 2 years of age. Offering teats/pacifiers and/or bottles to infants (p<0.001) and having prenatal consultations in the private network (p=0.013) were the factors most closely related to early weaning. Discussion: The prevalence of EBF was similar to current data and higher than older studies and the target set by the World Health Organization (WHO). Conclusion:The presented results demonstrate that the guidance and dissemination of information about BF by health professionals is still deficient, requiring expansion of health promotion actions aimed at pregnant and breastfeeding women in both the public and private sectors.