Unemployment and precarious employment (PE) are routinely found to be associated with poorer mental health. Importantly, women are over-represented in PE (due to disproportionate unpaid care demands), yet a gender lens has been lacking in much of the extant literature. This study addresses several gaps by reconsidering how PE can be conceptualised from a gender perspective and examining the impact of differing levels of multidimensional PE on the mental health of working-age Australians. Utilising sixteen annual waves (2005–2020) of the HILDA survey, this longitudinal study employed mixed-effects analysis and Mundlak modelling to examine the association between PE and mental health in working-age (25–64yrs) adults. Mental health was assessed using the MHI-5 scale. A multidimensional PE scale (based on objective and subjective indicators) was developed and three levels of precarity were modelled. 19,442 participants were included in the analyses and all models were stratified by gender. We found women experience greater exposure to PE in Australia, and our results showed a ubiquitously strong and negative association between PE and mental health in both women and men, across all levels of PE, with a dose dependent association observed with increasing PE. Additional adjustment for prior mental health slightly attenuated effect sizes, but the strength and direction of all associations were unchanged. This study provides longitudinal evidence of the detrimental impact of PE on the mental health of working age Australians, highlighting the importance of labour regulations and employment policies to minimize PE for all adults. However, given women's differential exposure to PE, this study also reinforces the urgent need for gender-sensitive social policies to address continued inequity in the division of unpaid household labour to promote a more equitable paid labour market into the future.