Aim: To determine whether having periodontitis is associated with cognitive decline among older adults. Material and Methods: A prospective population study of older adults, Swedish National Study on Ageing and Care, (SNAC) provided repeated registrations of cognitive functions. Cognitive decline was defined as ≥3-points deterioration from a predetermined level at baseline, using the Mini-Mental State Examination (MMSE). Between 2001 and 2003, 715 individuals had a medical as well as a clinical and radiographic dental examination. The individuals were re-examined after 6 years. Periodontitis was defined as ≥4 mm bone loss at ≥30% of tooth sites. Social variables were captured from questionnaires. Results: The multivariate logistic regression analysis demonstrated a statistically significant association between prevalence of periodontitis and cognitive decline after adjustments of confounding factors of importance. Conclusions: A history of periodontitis may be of importance for cognitive functions among older adults. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd