Across the United States, many faculty members are developing new mixed re-search courses. However, before embarking on teaching these courses, it would be helpful for instructors to be aware of the challenges faced by instructors and students in mixed research courses. Thus, the purpose of this qualitative-dominant mixed research study was to document these challenges. Participants were 11 instructors of mixed research courses from institutions around the United States who were selected purposively via critical case sampling such that they represent-ed a diverse set of instructors. The following four themes emerged that represent-ed dimensions of challenges: Time, Diversity, Format/Life Situations, and Pre-conceived Bias. Three of these themes yielded 10 sub-themes. Moreover, a correspondence analysis of the four themes revealed that they each fell somewhere on a continuum that lay from internal influences that characterized an interaction be-tween instructors and students (i.e., Diversity, Format/Life Situations) to external influences that characterized an interaction between instructors and curricula pertaining to the rapidly evolving field of mixed research--yielding the meta-themes of Internal Influence and External Influence. Implications for instructors and students undertaking mixed research courses are discussed.