Work is a fundamental social determinant of health that profoundly shapes health outcomes and drives health inequities. Understanding how employment relations—particularly precarious work—affect occupational and mental health is essential for advancing health equity. This chapter critically examines the structural and psychosocial mechanisms linking precarious employment to health inequalities. Drawing on insights from the PRESME Commission on Precarious Work and Mental Health and the EMCONET Report on Employment, Work and Health Inequalities, it situates precarious work within the broader context of neoliberal labor market transformations that have eroded social and employment protections. The chapter differentiates between employment conditions (e.g., job security, rights, income, and benefits) and working conditions (e.g., physical, psychosocial, and organizational risks), emphasizing how both dimensions interact to produce differential exposures and susceptibilities across social class, gender, age, ethnicity, and migration status. It also advances a theoretical framework that integrates political economy, occupational health psychology, and social epidemiology to explain how precarious work undermines health through mechanisms of chronic stress, insecurity, and social disempowerment. Finally, the chapter calls for comprehensive public health and labor policies that confront the structural drivers of precarious employment—ensuring decent work, fair wages, and universal access to social protection—while addressing the ecological and economic crises that sustain precarious work. By centering the social and political determinants of work, this framework contributes to rethinking occupational health research and policy toward greater justice, sustainability, and well-being.