Client advocacy is defined as the intentional actions of professional counselors to assist in removing barriers that clients face to promote well-being and/or growth and development. Without client advocacy, there is risk of not helping clients reach their full potential. Professional counselors are responsible for advocating with and for clients. The ultimate goal is to empower clients to be better advocates for themselves. In this chapter, theoretical foundations of client advocacy will be discussed that include oppression and discrimination, empowerment, social action, characteristics of effective client advocates, advocacy competencies, and professional organizations’ views of client advocacy. Additionally, ethical and professional standards from codes of ethics and CACREP standards regarding advocacy will be described. An integrated model of client advocacy will be discussed, which includes multicultural competencies, advocacy competencies, and client wellness. This chapter will also explore applications of client advocacy to increase understanding of advocacy through clinical practice and supervision. A case study with a client using the Indivisible Self Model is outlined to provide guidance on how to promote client wellness and interventions are described that address client empowerment, community collaboration, and collective action.