We investigated the influence of collaborative learning on students' openness to diversity in the 1st year of college. Even in the presence of a host of potential confounders, we found that exposure to collaborative learning activities positively influenced students' openness to diversity, regardless of their individual background characteristics. Further, this relation was mediated through students' interactional diversity experiences. That is, exposure to collaborative learning led to a greater frequency of students interacting with others who were different from themselves, which in turn led to greater openness to diversity.