Aim: The influence of non-surgical periodontal therapy on oral health-related quality of life (OHQoL) was investigated. Materials and Methods: Sixty-five Chinese adults (25 men, mean 47.4 years) with moderate-to-advanced chronic periodontitis were recruited. All received oral hygiene instructions (OHI) and non-surgical periodontal treatment in a quadrant-wise approach, followed by recalls at 1, 3, 6, 9 and 12 months post treatment, when OHI and prophylaxis were repeated. Clinical parameters were recorded, and oral health impact profile short-form (OHIP-14S) was administered at all time points. Results: Moderate-to-deep sites (>= 4 mm) decreased from 31.0% to 3.0% at 12 months post treatment (p < 0.005) which corresponded well with reductions in plaque, 72.8% to 25.4% (p < 0.005) and bleeding on probing, 86.3% to 32.0% (p < 0.005). Median OHIP-14S scores gradually reduced from 17 at baseline to 14 over the first 6 months and remained plateaued at 12-month post treatment (p < 0.005). Improvements in subdomains of physical pain, psychological discomfort and psychological disability accounted for the changes. Conclusion: This study demonstrates that OHQoL, in particular, pain and psychological subdomains, improvement was associated with non-surgical periodontal therapy responses. Clinicians could capitalize upon the positive psychological OHQoL impacts of mechanical periodontal treatment for subsequent patient-centred motivation during maintenance therapy.