This was a cross-sectional study to investigate predisposing factors associated with delirium among demented long-term-care residents and to assess the cumulative effect of these factors on the likelihood of having delirium. Of the 155 participants, 109 (70.3%) were found delirious according to the confusion assessment method. Among these individuals, age (OR = 1.07; 95% CI = 1.05-1.10) and severity of dementia (OR = 1.05; 95% CI = 1.03-1.07) were the most associated factors of delirium. The likelihood of being in delirium increased with the number of associated predisposing factors present (OR = 1.67; 95% CI = 1.11-2.51). Associated factors identified were level of functional autonomy, pain, depression, behavioral disturbances, number of medications, dehydration, fever, and malnutrition. Identification of predisposing factors will help nurses in detecting those residents in long-term care settings who are at high-risk for delirium, as well as in designing preventive intervention strategies for delirium, based on these factors.