Objectives Vitamin D plays an essential role in bone metabo- lism as well as in immunity. Hence, it might affect the devel- opment and extent of periodontal disease. The aim of this study was the assessment of 25-hydroxyvitamin D (25(OH)D) status in periodontal disease. Materials and methods Twenty-nine patients with severe periodontal disease and 29 healthy volunteers were recruited in this case-control-study. Serum 25(OH)D levels, Periodontal Probing Depth (PPD), Clinical Attachment Level (CAL), Bleeding on Probing (BOP), Body Mass Index (BMI), and current smoking status and smoking history (packyears) were assessed in all participants. Serum 25(OH)D levels were com- pared between controls and cases. Multivariable logistic regression was used to determine the odds ratio (OR) and 95 % confidence interval (CI) for periodontal disease in 25(OH)D deficient probands. Results Patients with periodontal disease presented a signifi- cantly higher proportion of deficient 25(OH)D levels (i.e., <50 nmol/l) compared to healthy controls (48 vs. 14 % respec- tively). The adjusted OR for periodontal disease with vitamin D deficiency was 1.5 (95 % CI, 1.13–1.98). No correlation between serum 25(OH)D levels and CAL, PPD, and BOP in the group with periodontal disease was found. Conclusions In this case-control-study 25(OH)D deficiency is significantly associated with periodontal disease. Clinical relevance The assessment of vitamin D levels in pa- tients presenting with periodontal disease seems advisable, as vitamin D deficiency might be involved in the onset and pro- gression of periodontal disease.