Public Significance Statement This paper provides a review of the perfectionism and depression research, models, and treatment approaches developed by Paul L. Hewitt, Gordon L. Flett, and Sam Mikail and colleagues. It argues for conceptualizing perfectionism as a core vulnerability factor in depression and outlines the extant treatment and an empirically suppported treatment for perfectionism and depression. Perfectionism is a personality style that has been described for decades as highly relevant to depression. Over the past 30 years, our work, as well as the work of other Canadian and international researchers, has attempted to understand the cause and maintenance of perfectionism and the role that this pernicious personality style plays in predisposing individuals to various problems, such as depression. In the present article, we outline our multidimensional and multilevel descriptive model of perfectionism and summarize several models of perfectionism and depression that we have focused on over the years, both from a diathesis-stress perspective and from a more complex developmental and relational perspective. We, then, outline the extant research that we and others have conducted based on these models and conclude by providing a description of and evidence for a dynamic-relational treatment of perfectionism that functions to reduce depressive symptoms and vulnerability to depression. Our article underscores the importance of perfectionism by discussing how it is involved both directly in creating a predisposition to depression and indirectly in precluding accessing, initiating, and benefitting from depression treatment.