Retirement is a life situation embracing 14 percent of the US population. Transitioning into and through it is a significant life challenge that does not always go well; sadly, for many, it can represent a “slough of despond,” a pathway that can spiral into depression. Retirement transition represents an inflection point where informed mental health practitioners can apply prevention competencies to help prospective retirees anticipate and prepare for success as well as those harness their resources in the early phases of retirement to avoid pitfalls and promote positive steps. Attention to financial and healthcare planning is important. But so is addressing a range of psychosocial considerations that typically lay fallow but are central to both a satisfying and meaningful retirement and the armamentarium of counseling psychologists and other helping professionals. This chapter details the application of evidence-based knowledge to concepts of transition and adjustment in retirement, phases of retirement (and where best to intervene), and how to holistically plan for prevention. Suggestions for social justice and future research in retirement transition conclude the chapter.