OBJECTIVE To (1) investigate dental anxiety (DA) and oral health-related quality of life (OHRQOL) before and after non-surgical periodontal treatment (NSPT) and (2) determine correlations between these patient-reported measures. METHODS Demographics, smoking habits, dental pain, Modified Corah's Dental Anxiety Scale (MDAS), and Oral Health Impact Profile (OHIP-14) were assessed in eighty-two participants. RESULTS Mean age was 48.3 years ± 11.5. At baseline, 8.5% reported being active smokers. Of non-smokers, 11% reported being an ex-smoker. After NSPT, 11.0% reported smoking. Patients' maximal pain in the last month decreased after therapy. Before treatment, participants reported higher DA. Extreme DA was observed in 8.5% of participants before therapy. Afterwards, 2.4% of participants reported extreme DA. Fear of having a foreign object in the mouth decreased after NSPT. All OHIP-14 scores, except functional limitation, improved post-treatment. Higher DA was associated with worse OHRQoL before treatment. After treatment, total MDAS score was associated with OHIP-14 global score, physical pain, psychological disability, and social disability. Worse MDAS sub-scores were associated with a higher OHIP-14 global score. Individuals with "normal/slight anxiety" had a significant improvement in OHRQoL, whereas people in the "moderate and extreme anxiety" group did not report a significant improvement. Patients diagnosed with generalized periodontitis (GP) stage III grade B and GP stage IV grade B reported less anxiety after NSPT. CONCLUSIONS Associations of MDAS subcategories with OHIP-14 domain scores were found before and after therapy. DA decreases and OHRQoL enhances after NSPT in patients with "normal/slight" anxiety to dental treatment. Dental practitioners should plan strategies to cope with anxiety to dental treatment and prevent decreases in OHRQoL. CONCLUSIONS Within the limitations of this study, DA and OHRQoL were positively correlated in patients with periodontitis, before and after NSPT, using the MDAS and OHIP-14 questionnaires. The results of our study suggest that treatment is effective in terms of alleviating DA and improving oral health, along with quality of life, in patients that report "normal/slight" anxiety to dental treatment. Nonetheless, results must be interpreted with caution since patients are generally anxious before any type of dental treatment. DA may not just be confined to NSPT per se. According to our results, evaluation of both outcomes should be an integral part of routine periodontal clinical evaluation and periodontal reevaluation of initial therapy. It is important that clinicians learn to identify patients that suffer from anxiety and take time to explain the treatment procedures to the patient, to strive for patient's emotional well-being before, during, and after dental care services. The use of specific questionnaires for both DA and OHRQoL may be more appropriate to demonstrate the psychological and quality of life differences due to periodontal disease and NSPT.