Purpose <p>The importance, value, and benefits of fostering mentally healthy workplaces are well established. The Indicators of a Thriving Workplace (ITW) questionnaire measures a range of individual psychological and organisational factors as lead indicators of workplace mental health. The current study aimed to develop a valid summary set of indicators or domains of workplace mental health to enable comparisons across industries and sectors nationally.</p> Methods <p>Exploratory factor analysis and principal components analysis were sequentially performed on survey data from two independent samples selected from a nationally representative and large (<i>n</i> = 9,947) cohort of Australian workers.</p> Results <p>Five domains of workplace mental health aligning with the integrated approach to workplace mental health emerged and were confirmed: Leadership, Connectedness, Safety, Work Design, and Capability. When average domain scores were compared across industry, small but statistically significant differences were identified.</p> Conclusion <p>The validation of these domains positions the ITW questionnaire as the first comprehensive measure of workplace mental health and well-being that focuses on thriving as a positive construct for Australian workers. Further, industry-based Domain profiling could provide a basis for the prioritisation of efforts to improve workplace mental health, with successful initiatives and practices perhaps adaptable to other industries. Interventions addressing workplace mental health are likely to be more successful when they are industry specific, although interventions responding to mental health challenges in the workplace, such as those tackling mental health-related stigma, may require less cross-industry tailoring.</p>