This chapter has three foci. First, it describes what stages athletes go through during their multi-year athletic career and also in their psychological, psychosocial, and academic-vocational development. The second and particular focus of this chapter is on career transitions as turning phases in career development. Successfully coping with athletic and non-athletic, normative (i.e., predictable) and non-normative (i.e., less predictable) transitions allows greater opportunity for an athlete to live a long and successful life in sport as well as being able to adjust effectively to the post-sports career. Alternatively, failure in coping with a transition leads to a crisis which is often followed by negative consequences such as premature dropout from sport, neurosis, alcohol/drug abuse, etc. The third focus of the chapter is on career assistance that is on a set of interventions helping athletes to optimize their career development and prepare for and/or cope with career transitions.