Purpose: To explore employment as a social determinant of health through examining the relationship between employment status and mental health. Method: The authors conducted a systematic review of 48 longitudinal studies conducted in Australia, Canada, Croatia, Germany, Ireland, Israel, the Netherlands, Norway, United Kingdom, and United States to explore the causal relationship between employment status and mental health. Results: Five common trajectories were identified as employment, unemployment, job loss, reemployment, and retired. Employment and reemployment were associated with better mental health (e.g., lower psychological distress, lower depression, lower anxiety), whereas unemployment and job loss were correlated with poorer mental health (e.g., higher depression, higher psychological distress). Conclusion: To enhance employment outcomes, service providers must acknowledge the relationship between employment status and mental health. The trajectories of employment and reemployment should be further explored by category (e.g., temporary, adequacy, income, skill level, hours, status). Additional research is needed to further elucidate the relationship between employment status and mental health.