Background: Explaining individual differences in people's attitudes toward individuals with intellectual disability (ID) is important for increasing social inclusion of people with ID. The aim of the current study was to replicate and extend past research by formulating a single model of attitudes toward individuals with ID with several predictors: personality traits, quality and quantity of contact, perceived knowledge of ID, social desirability, and demographics. Background: Methods: A sample of 221 undergraduate students in the United States completed several surveys in a lab setting: the Mental Retardation Attitude Inventory--Revised, the Big Five Inventory, McManus et al.'s measures of contact with and perceived knowledge of ID, and the Marlowe-Crowne Social Desirability Scale. Methods: et al. Results: Results replicated previous findings by showing quality of contact was the strongest predictor of attitudes. Additionally, we found openness to experience and agreeableness remained significant predictors after holding all other variables constant. A follow-up mediation analysis demonstrated that quality of contact mediated the relations from openness and agreeableness to attitudes. Results: Conclusions: Findings suggest personality factors can influence attitudes toward individuals with ID, and further emphasize the importance of quality of contact. Implications for the social inclusion of individuals with ID are discussed. Conclusions: Findings suggest personality factors can influence attitudes toward individuals with ID, and further emphasize the importance of quality of contact. Implications for the social inclusion of individuals with ID are discussed.