Background: Oral opportunistic bacteria pose health risks for people with intellectual disability, yet their relationship with activities of daily living (ADLs) remains underexplored. Methods: We conducted a cross-sectional study of 178 institutionalised people with intellectual disability. ADL was assessed by caregivers. Oral samples were collected non-invasively and analysed via culture-based methods. Student's t-test, Fisher exact test, and logistic regression were used to examine associations between ADL and oral pathogens. Results: Interestingly, individuals with intellectual disability and higher ADL scores exhibited a greater prevalence of oral opportunistic bacteria, notably "Klebsiella pneumoniae" (15.7%) and "Prevotella melaninogenica" (14.7%). No significant associations were found with demographic variables. Conclusions: Functional independence does not equate to adequate oral hygiene among people with intellectual disability. Enhancing self-care training, providing caregiver-assisted support, and increasing outreach dental services are recommended to mitigate oral health risks. Culture-based methods offer a practical approach for identifying bacterial presence in resource-limited settings.