Background: Carbohydrate Counting (CC) is important in managing the treatment of Type 1 Diabetes Mellitus (T1DM). This study aimed to evaluate the factors associated with adherence to CC in adults with T1DM in Brazil. Methods: A cross-sectional study was conducted through an online questionnaire. Information was collected on sociodemographic, economic, clinical, and anthropometric factors; knowledge of the CC strategy; the acquisition of supplies; the perception of mathematical skills as a hurdle in adhering to CC; and follow-up with healthcare professionals. Pearson’s chi-squared or Fisher’s exact test was applied (p < 0.05). Results: Of the 173 participants, 72.8% practiced CC. Practicing CC was associated with having an income higher than three minimum wage equivalents (p = 0.023), and not practicing CC due to the lack of supplies for glucose monitoring was associated with having practiced CC at some point but is currently not practicing (p < 0.001). Not practicing the necessary calculations for CC was associated with “knowing how to do CC but had never done it” and “had done CC at some point but currently not practicing” (p < 0.001). Stopping or having stopped practicing CC due to insufficient materials for glucose monitoring was associated with having practiced CC for a period but is not currently doing so (p < 0.001). Following up with healthcare professionals (p < 0.001) and receiving encouragement from the endocrinologist (p < 0.001) and nutritionist (p = 0.047) were associated with adherence to CC. Conclusions: Having a better financial status, performing the mathematical calculations required for CC, having access to supplies for glucose monitoring, and receiving specialized professional follow-up were factors associated with adherence to CC in Brazil.