Periodontal disease negatively affects oral health-related quality of life (OHRQoL). While there is sufficient evidence for the clinical efficacy of periodontal therapy, data on patient-based outcomes are limited. To systematically review the available evidence on the impact of periodontal therapy on OHRQoL in adults. MEDLINE, EMBASE, CENTRAL and LILACS were searched without language restrictions. Longitudinal observational and intervention studies assessing changes in OHRQoL using validated measures, in adults with periodontal disease undergoing non-surgical (NST) or surgical therapy (ST), were eligible for inclusion. Study quality was assessed using the Newcastle-Ottawa scale and CONSORT-checklist. No meta-analysis was performed. Eleven studies (seven prospective case-series', one controlled before-after study and three randomized controlled trials) of "medium" methodological quality were included in the review. All studies reported impaired OHRQoL before therapy. Nine studies reported a statistically significant improvement in OHRQoL after NST (follow-up = 1 week to 12 months, p < 0.05). The effect size for this improvement ranged from small (0.27) to large (0.8). No significant differences were reported between different forms of NST. Surgical therapy had a relatively lower impact on OHRQoL. A correlation between poor clinical response to therapy and poor OHRQoL outcomes was observed. Routine non-surgical therapy can moderately improve the OHRQoL in adults with periodontal disease. © 2012 John Wiley & Sons A/S.