Background/Aims: Adverse drug events (ADEs) are a frequent problem encountered in the elderly. The aim of this study was to elucidate the factors that influence ADEs in an elderly population with cognitive impairment. Methods: 242 patients were recruited from dementia clinics and assessed after 6 months for ADEs. The use of natural health products (NHPs) was also documented. Results: Backward logistic regression found that higher age (OR = 1.06; 95% CI 1.01–1.12), and greater cognitive impairment (OR = 0.94; 95% CI 0.90–0.98) were associated with an increased risk of developing an ADE while the use of NHPs (OR = 0.32; 95% CI 0.13–0.79) was associated with a decreased risk (χ2 = 27.6, p < 0.001). Conclusion: Risk of ADEs increased with greater age and cognitive impairment but decreased with the use of NHPs.