We aimed to clarify the physical factors associated with the incidence of aspiration pneumonia in a community-based integrated care unit. This retrospective cohort study included 412 patients aged 65 years or older admitted to a community-based integrated care unit. A new diagnosis of aspiration pneumonia made by the attending physician based on physical examination, imaging findings, and blood test data after 48 h of admission was considered as an incidence of aspiration pneumonia. Basic patient information, activities of daily living, swallowing function, nutritional status, cognitive function, oral health-related factors, and energy intake were retrospectively investigated. We classified the patients into a pneumonia group and a non-pneumonia group, and examined the factors associated with the development of aspiration pneumonia. The mean age was 86.9 ± 8.1 years, and the pneumonia group comprised 49 participants. Comparison between the groups showed significant differences in oral environment, denture use, cognitive functional independence measure, and discharge to home. In multivariate logistic regression analysis, oral environment (odds ratio (OR) = 0.229, 95% confidence interval (CI): 0.070–0.753, p
= 0.015) and use of dentures (OR = 0.360, 95% CI: 0.172–0.754, p
= 0.007) were independently associated with aspiration pneumonia. Oral care and the use of dentures may be effective in preventing aspiration pneumonia.