This paper presents an instrument for assessing a client’s level of acculturation. The instrument has been designed for use by social work clinicians working with clients that affiliate or identify with a culture of origin that differs from mainstream culture in the United States. This bilinear, multidimensional instrument is composed of thirty indicators organized into three domains: language, cultural behavior, and cultural knowledge. Existing research that informed the domain selection is reviewed and the rationale behind the inclusion of each indicator is given. The instrument is presented in such a way as to show how it should be adapted or augmented as needed by practitioners in their work with clients. The paper shows how instrument is designed to: (1) increase practitioner understanding of a client’s degree of acculturation; (2) increase the practitioner’s cultural awareness and sensitivity; and (3) increase the practitioner’s recognition of the impact of acculturation on other health, psychological, and behavioral outcomes and health and social service utilization.