This chapter introduces the systems theory framework (STF) of career development (McMahon & Patton, 1995; Patton & McMahon, 1999, 2006, 2014, 2015, 2017, 2018). The STF incorporates systemic thinking and systemic mapping to portray career development as a dynamic and complex process negotiated by individuals in the context of their systems of influence. The STF provides a conceptual and practical map through which career development practices, such as career counselling and career education, may be systemically conceptualised. Career practitioners are encouraged to apply systemic thinking in their work in order to accommodate the context, complexity, and cultures of their clients’ career development.