In this chapter, concepts and history of assessment and testing in the context of Aboriginal and Torres Strait Islander social and emotional wellbeing and mental health are discussed. Importantly, recently revised diagnostic guidelines and the National Practice Standards for the Mental Health Workforce 20131 and their appropriateness for meeting the distinctive needs of Aboriginal people are reviewed. Various assessment tools and measures that have been validated or proved appropriate for use with particular Aboriginal populations, i.e. youth, women and older people, are described. We conclude that practitioners need to be critically reflective in their role in assessment, and position themselves to play an important transformative role in conducting assessment. This extends to acknowledging and enacting culturally responsive principles, procedures and practices to ensure that Aboriginal people have access to effective, culturally secure mental health care.