Background: The development of cultural competence is central to the therapeutic alliance with clients from diverse backgrounds. Given that the majority of Australia’s population growth is due to migration, mental health practitioner construing of non-White and White people has a significant role and impact on client engagement. Method: To examine the impact of mental health practitioner construing on their strategies for cultural competence and the therapeutic alliance, 20 White and non-White mental health practitioners and trainees providing mental health services were purposively sampled and interviewed face-to-face or via videoconferencing. Data was analysed thematically and the impact of construing on practitioner cultural competence and the therapeutic alliance were interpreted using Personal Construct Psychology. Results: Practitioners demonstrated cultural competence in their acknowledgement of the impact of negative construing of ethnic, cultural, religious, social, racial and linguistic diversity on client wellbeing. Practitioners sought to address these negative impacts on clients by drawing on the client-practitioner relationship to improve the therapeutic alliance. Conclusions: The results reinforce the need for mental health care workers to develop cultural competence with a focus on developing awareness of the impact of frameworks of Whiteness on the experiences of non-White people. This is central to the development of a therapeutic alliance where clients feel understood and assured that their mental health concerns will not be constructed (and treated) through a framework that constrains both White and non-White people’s opportunities for improved mental health and wellbeing.