Interest in sustainable careers has grown substantially in recent decades as a host of external and personal forces has increasingly disrupted individuals' continued employment or diminished the quality of their experiences at work. However, there is a lack of consensus regarding the definition and measurement of career sustainability that limits our understanding of the career sustainability process. In this article, we propose a definition that we believe represents the essence of career sustainability and make recommendations regarding the assessment of the construct. We then present a research agenda that includes a framework to guide research on the career sustainability process and identifies areas where future research attention is warranted. We conclude with a discussion of the implications of the framework for counseling practice.