The focus of this chapter is the evolution of social work's quest to achieve understanding of the meaning of and conditions for the development and application of cultural competence by practitioners in relation to assessment and intervention in the context of diverse client populations. To grasp social work's progression toward the achievement of this goal, it is important to understand the core theories and main principles that guide the profession. Central in this core is the person-in-the-environment (PIE) approach. PIE was born early in the development of social work as a profession on the basis of charity work with immigrants in the settlement houses. Two distinct approaches to the helping process emerged. One approach adopted a community oriented viewpoint and focused on social action whereas the other emphasized meeting the needs of individual clients (Shulman, 2006). Those who embraced the social action approach became advocates for the oppressed and fought against poor housing and child labor as well as for better health services (Walsh, 2009). Those who were more focused on individual needs are credited with the development of currently commonly used models for helping individuals and their families (Shulman, 2006). The combined professional mission of serving individual concurrent with being agents for social change is what defines the very nature of social work today and differentiates it from other helping professions.