Background The study objective was to evaluate the effects of professional continuous glucose monitoring (CGM) as an adjuvant educational tool for improving glycemic control in patients with type 2 diabetes (T2D). Methods We conducted a three-month quasi-experimental study with an intervention (IGr) and control group (CGr) and ex-ante and ex-post evaluations in one family medicine clinic in Mexico City. Participants were T2D patients with HbA1c > 8% attending a comprehensive diabetes care program. In addition to the program, the IGr wore a professional CGM sensor (iPro™2) during the first 7 days of the study. Following this period, IGr participants had a medical consultation for the CGM results and treatment adjustments. Additionally, they received an educational session and personalized diet plan from a dietitian. After 3 months, the IGr again wore the CGM sensor for 1 week. The primary outcome variable was HbA1c level measured at baseline and 3 months after the CGM intervention. We analyzed the effect of the intervention on HbA1c levels by estimating the differences-in-differences treatment effect (Diff-in-Diff). Additionally, baseline and three-month CGM and dietary information were recorded for the IGr and analyzed using the Student’s paired t-test and mixed-effects generalized linear models to control for patients’ baseline characteristics. Results Overall, 302 T2D patients participated in the study (IGr, n = 150; control, n = 152). At the end of the three-month follow-up, we observed 0.439 mean HbA1C difference between groups (p = 0.004), with an additional decrease in HbA1c levels in the IGr compared with the CGr (Diff-in-Diff HbA1c mean of − 0.481% points, p = 0.023). Moreover, compared with the baseline, the three-month CGM patterns showed a significant increase in the percentage of time in glucose range (+ 7.25; p = 0.011); a reduction in the percentage of time above 180 mg/dl (− 6.01; p = 0.045), a decrease in glycemic variability (− 3.94, p = 0.034); and improvements in dietary patterns, shown by a reduction in total caloric intake (− 197.66 Kcal/day; p = 0.0001). Conclusion Professional CGM contributes to reducing HbA1c levels and is an adjuvant educational tool that can improve glycemic control in patients with T2D.