Background: Although epidemiological data suggest an association between periodontitis (PD) and peripheral arterial disease (PAD), it is currently unclear whether treatment of PD influences the severity of PAD. Patients and methods: Whether periodontal treatment is associated with PAD disease severity was examined by analysing health insurance claims data of patients insured by the German health insurance fund, BARMER, between January 1, 2012 and December 31, 2016. The presence of PAD was determined in individuals using International Classification of Diseases (ICD) 10th revision codes for intermittent claudication (IC) or chronic limb threatening ischaemia (CLTI). Treatment of PD was assessed by adequate ambulatory coding for non-surgical and surgical treatment of PD. Multivariate logistic regression analysis was performed to evaluate the association between PAD stages and periodontal treatment, adjusted for diabetes, age and sex. Results: The study cohort included 70,944 hospitalized patients with a diagnosis of symptomatic PAD (54.99 % women, 49.05 % IC). Among these patients, 3,567 (5.03 %) had received prior treatment for PD by supra- or sub-gingival debridement. PAD patients who had received periodontal treatment showed a lower proportion of CLTI (28.76 % among treated vs. 52.12 % among non-treated). Using multivariable regression methods, exhibiting a CLTI (vs. IC) was associated with not being treated for PD (Odds Ratio 1.97, 95 %-CI 1.83-2.13) after adjustment for age, gender, and diabetes. Conclusions: In this large-scale retrospective analysis of health insurance claims data comprising hospitalized symptomatic PAD patients, treatment of PD was associated with PAD disease severity independent of age, gender and diabetes. A potential benefit of periodontal treatment in relation to PAD will have to be determined in further prospective studies.