Aim Growing evidence suggests that tooth loss is associated with increased risk of stroke. In the current study, we investigated cumulative medical costs related to stroke using data from the Advanced Elderly Medical Service System. We hypothesized that tooth loss was associated with an increase in medical costs related to stroke among older Japanese adults. Methods A total of 273 Japanese adults aged 80 years were enrolled in the current study. Baseline medical and dental examinations were carried out in June 2008. Medical care use and costs were monitored by linkage with National Health Insurance claim files from baseline to the end of February 2011. Medical costs related to stroke per month were calculated and examined for any association with the baseline number of remaining teeth using a linear regression model with robust standard errors. Results A total of 19 individuals were admitted to hospital for stroke during the follow‐up period. A significant negative association was found between the number of teeth and medical costs related to stroke per month. The regression coefficients of the number of teeth in relation to medical costs related to stroke was −248 (95% CI −438 to −58, P = 0.011) in the crude model and −226 (95% CI −413 to −38, P = 0.018) after adjusting for other confounders. Conclusion Within the limitations of the present study, the reported findings suggest an independent relationship of tooth loss with increase in medical cost related to stroke among older Japanese adults. Further studies are necessary to substantiate these findings. Geriatr Gerontol Int 2017; 17: 202–210.