The taking up of an "educative" mantle has proven to be a complex task for museums, filled with many unknown and/or misunderstood factors. Of the vast assortment of educational opportunities museums afford their adult patrons and staff, the majority fall into one or two learning categories: either they are nonformal or informal. In effort to provide a clearer understanding of adult nonformal and informal learning in museums, this literature review aims to address both conceptual and empirical literature that explores nonformal and informal contexts of learning within museum settings. We employed academic search engines including Dissertation Abstracts, Web of Science, ERIC, ProQuest Direct, and ABI to identify museum research, as well as citation searchers, to select the papers for review. We found themes within both the nonformal and informal literatures. Themes in nonformal learning include staff and volunteer nonformal learning, and visitors' nonformal learning. Within the informal learning literature we found the themes addressing how individuals influence their own museum learning and how museums influence visitor learning. A review of the literature revealed that existing literature on adult learning in museums suffers greatly from research that is neither theory-informed nor theory-generating, and there is a strange absence of adult education and learning theory in museum studies. (Contains 36 notes.)