To examine whether chewing ability affects healthcare use and expenditure and whether improving dietary quality alleviates any such effects.Prospective cohort.The Elderly Nutrition and Health Survey in Taiwan (1999-2000), a nationwide community-based survey of people aged 65 and older.Individuals aged 65 and older (N = 1,793; 903 men, 890 women).Chewing ability (satisfactory or unsatisfactory) was assessed using a questionnaire, and dietary quality was assessed using a 24-hour dietary recall as a dietary diversity score. Data on annual medical use and expenditures from the interview date until December 31, 2006, were collected from National Health Insurance claims. Generalized linear models were used to assess the associations between chewing ability, dietary quality, and annual medical usage or expenditure.After 8 years of follow-up, older adults with unsatisfactory chewing ability had considerably higher emergency, hospitalization, and total medical expenditures. Older adults with unsatisfactory chewing ability and a poor diet used fewer annual preventive care and dental services than those with satisfactory chewing ability but had longer hospital stays and higher expenditures. After adjusting for covariates, unsatisfactory chewing ability resulted in significantly longer hospital stays in participants with a poor diet (β = 2.34, 95% confidence interval = 2.02-2.71, P < .001).Unsatisfactory chewing ability and a less-diverse diet together are associated with longer hospital stays and higher medical expenditures.