This article reports on an integrative literature review of the self-study research published between 2009 and 2021 and examines how authors defined, enacted, and addressed validity within the self-study literature. We follow the example provided in the 2004 article by Feldman, Paugh, and Mills in order to gain more insights into the distinctions between self-study and action research by comparing and contrasting these 'parallel' modes of research. In addition, we constructed a visual representation to highlight the overlap between the featured methodologies in this review. Implications specific to the parallel approaches of self-study and action research are discussed.