OBJECTIVE: This study aimed to assess the relationship between oral hygiene/stomatognathic function and residual intraoral medication in older adults and to identify the oral factors associated with residual oral medication. METHODS: The study included 309 older adults (77 men, 232 women, mean age: 74.1 ± 7.4 years) who were prescribed medications at regular intervals. The following survey items were assessed: overall physical condition, intraoral condition and oral function. Participants prescribed oral medication were classified into groups with and without residual medication in the oral cavity. Statistical analysis was performed using univariate analysis for each of the factors contributing to the presence of residual medication. RESULTS: Only 1.9% of all patients had residual medication, which suggests that older adults in this survey had a low risk of residual intraoral medication. However, greater attention should be given to residual intraoral medication in older adults receiving long-term care. Powdered-form oral medications were more likely to remain in the oral cavity. Older adults with residual medication had a tendency to have less occlusal support, poor tongue hygiene and poor tongue movement. Oral function, particularly functions that are closely related to swallowing, was significantly lower in the residual intraoral medication group when compared to those of the group without residual intraoral medication. CONCLUSIONS: Reduced oral function and powered medication were associated with greater residual intraoral medication in this sample of older Japanese adults.