Background: Racial, ethnic, religious, and cultural diversity in Australia is rapidly increasing. Although Indigenous Australians account for only approximately 3.5% of the country’s population, over 50% of Australians were born overseas or have at least one migrant parent. Migration accounts for over 60% of Australia’s population growth, with migration from Asia, Sub-Saharan African and the Americas increasing by 500% in the last decade. Little is known about Australian mental health care practitioners’ attitudes toward this diversity and their level of cultural competence. Aim: Given the relationship between practitioner cultural competence and the mental health outcomes of non-White clients, this study aimed to identify factors that influence non-White and White practitioners’ cultural competence. Methods: An online questionnaire was completed by 139 Australian mental health practitioners. The measures included: the Balanced Inventory of Desirable Responding (BIDR); the Multicultural Counselling Inventory (MCI); and the Color-blind Racial Attitudes Scale (CoBRAS). Descriptive statistics were used to summarise participants’ demographic characteristics. One-way ANOVA and Kruskal–Wallis tests were conducted to identify between-group differences (non-White compared to White practitioners) in cultural competence and racial and ethnic blindness. Correlation analyses were conducted to determine the association between participants’ gender or age and cultural competence. Hierarchical multiple regression analysis was conducted to predict cultural competence. Results: The study demonstrates that non-White mental health practitioners are more culturally aware and have better multicultural counselling relationships with non-White people than their White counterparts. Higher MCI total scores (measuring cultural competence) were associated with older age, greater attendance of cultural competence-related trainings and increased awareness of general and pervasive racial and/or ethnic discrimination. Practitioners with higher MCI total scores were also likely to think more highly of themselves (e.g., have higher self-deceptive positive enhancement scores on the BIDR) than those with lower MCI total scores. Conclusion: The findings highlight that the current one-size-fits-all and skills-development approach to cultural competence training ignores the significant role that practitioner diversity and differences play. The recommendations from this study can inform clinical educators and supervisors about the importance of continuing professional development relevant to practitioners’ age, racial/ethnic background and practitioner engagement with prior cultural competence training.