Career development is underpinned by an extensive body of theory dating back more than a century and emanating from disciplines such as vocational psychology, sociology, and organisational psychology. Theories reflect the time, culture, and discipline in which they were developed. In response to dramatic changes in the labour market, globalisation, internationalisation, and greater cultural diversity, new theories continue to be formulated to account for the complex phenomenon of career development. Career theory and practice are inextricably related. Practice informs theory and career theory may assist practitioners to conceptualise cases and identify appropriate interventions. This chapter’s aim is to overview the origins and history of career development theory.