Aim: To evaluate glycosylated hemoglobin (HbA1c) before and after non-surgical periodontal treatment in patients with type 2 diabetes mellitus (DM-2). Methods: Twenty subjects diagnosed with periodontitis and DM-2 were treated using an NSPT protocol. Periodontal examination and blood measurements were performed at baseline and after three months. Patients with DM-2 treated for at least a year, with at least 10 teeth and with probing depths between 4-6 mm in more than three regions were included. The variables evaluated were HbA1c in blood and periodontal measures (probing depths, insertion level, gingival bleeding on probing, dental plaque, calculus, inflammation, clinical attachment and mobility). All patients were informed of the conditions of the therapy used. Scaling and root planning (SRP) of the full mouth was performed using an ultrasonic scaler and hand instrument under local anesthesia, supragingival prophylaxis and oral hygiene instruction. Also, 0.12% chlorhexidine digluconate was formulated twice a day for two weeks. Statistical analyses were performed using StataIC 14. The values are shown as the mean, median and standard deviation (SD) or interquartile rank (IR), and p<0.05 was considered significant. Results: Twenty subjects completed the three-month follow-up and were included in the analysis. Three months after the non-surgical periodontal treatment, most periodontal parameters had a meaningful reduction (p< 0.05) and a large effect size >0.8. Clinical attachment level showed no improvement. The HbA1c values were not significantly decreased (p=0.94). Conclusions: Although non-surgical periodontal therapy eliminates local inflammation, it is insufficient to significantly reduce HbA1c levels in a short time period.