The aim of this study is to investigate whether 25-hydroxyvitamin D (25(OH)D) is associated with periodontitis and tooth loss in older adults. A total of 2346 adults underwent a detailed dental examination as part of the health assessment of a national population study – The Irish Longitudinal Study of Ageing. 25(OH)D analysis was performed on frozen non-fasting total plasma using LC-MS. The analysis included both multiple logistic regression and multinominal logistic regression to investigate associations between 25(OH)D concentration, periodontitis and tooth loss, adjusting for a range of potential confounders. Results of the analysis found the mean age of participants was 65·3 years (sd 8·2) and 55·3 % of the group were female. Based on the quintile of 25(OH)D concentration, participants in the lowest v. highest quintile had an OR of 1·57 (95 % CI 1·16, 2·13; P < 0·01) of having periodontitis in the fully adjusted model. For tooth loss, participants in the lowest v. highest quintile of 25(OH)D had a RRR of 1·55 (95 % CI 1·12, 2·13; P < 0·01) to have 1–19 teeth and a RRR of 1·96 (95 % CI 1·20, 3·21; P < 0·01) to be edentulous, relative to those with ≥ 20 teeth in the fully adjusted models. These findings demonstrate that in this cross-sectional study of older men and women from Ireland, 25(OH)D concentration was associated with both periodontitis and tooth loss, independent of other risk factors.