Provider-enacted stigma is a barrier for people with substance use disorder (SUD) who interface with the healthcare system, and it has been shown to lead to worse healthcare outcomes. This has given urgency to the need for stigma reduction interventions such as education- and contact-based approaches. The positive effect of interprofessional education (IPE) in reducing graduate health students' stigmatizing attitudes on opioids has been examined before, and we contribute to the existing literature by examining the attitudes across the following four health disciplines-osteopathic medicine, physician assistant (PA) studies and public health, pharmacy, and nursing-following a single half-day IPE event focused on opioid use disorder (OUD). We aimed to determine whether attitudes could be affected by the IPE event by assessing attitudes utilizing an adapted version of the Alcohol and Alcohol Problems Perceptions Questionnaire (AAPPQ) before and after the IPE event. A total of 647 students across the four previously mentioned health disciplines participated in the IPE event. Attitudes were compared between the pre/post groups utilizing unpaired t tests, and a summative "all-attitudes" score was generated, with higher scores being associated with improved attitudes toward individuals with an OUD. Linear regression was performed controlling for program type, gender, and previous OUD exposure (personal, professional, and education). We found that the pre/post summative attitudes scores improved an average of 2.81 units (SD 0.87, p=0.001, CI 1.09-4.52) for the entire cohort of graduate health students (56.9 vs. 66.6, p<0.0001) and for all attitudinal subscales (roleadequacy, role legitimacy, role support, task-specific self-esteem, and work satisfaction). Students from PA programs had significantly higher attitude scores than other programs, and there were differences in degree type on attitude scores, with an average decrease of 1.89 units in attitude scores (SE 0.38, p<0.0001, CI-2.64 to-1.16). We found that students with previous exposure to OUD had higher pre-IPE event scores than those without, and knowing someone impacted by an SUD was a significant predictor of increased attitude scores, by an average of 3.82 units (SE 0.27, p<0.0001, CI 3.49-4.16). However, students without previous exposure to OUD had equal attitude scores post event to those who had previous exposure to OUD through education, personal experience, or training. Our findings suggest that an IPE intervention and panel discussion may improve attitudes toward people with OUD in healthcare trainees, which is consistent with previous research that shows the beneficial effect of education and contact in reducing stigma. Degree type and knowing someone who has been impacted by an SUD are also significant predictors of attitude scores. IPE events are useful in targeting a public health issue by encouraging collaboration between different health professionals at early stages of their training, and preclinical educational efforts can affect therapeutic attitudes.