Objectives Long working hours and precarious employment are relatively common in South Korea. Since both can impact on mental health, this study examined their independent and combined effects on depressive symptoms of employees.

Methods Data were from the Korean Welfare Panel Study (KOWEPS), 2010–2013. A total of 2733 full-time employees without depressive symptoms were analysed. Hierarchical logistic regression models were used to investigate the effect of the number of working hours per week (eg, 35–40 hours, 41–52 hours, 53–68 hours, and >68 hours) and employment status (permanent vs precarious employment) on depressive symptoms, measured using the Center for Epidemiological Studies Depression (CES-D) 11 scale.

Results Compared with individuals working 35–40 hours/week, employees working above 68 hours (OR 1.57, 95% CI 1.05 to 2.34) had higher odds of depressive symptoms after full adjustment. Similarly, precarious employees (OR 1.34, 95% CI 1.02 to 1.75) showed worse mental health than permanent employees. In the combined effect model, employees in precarious employment who worked above 68 hours/week (OR, 2.03 95% CI 1.08 to 3.83) exhibited the highest odds of depressive symptoms compared with permanent employees working 35 to 40 hours/week.

Conclusions Long work hours and precarious employment status were associated with higher odds of depressive symptoms. The findings highlight the importance of monitoring and addressing the vulnerable groups of employees to reduce the mental health burden of economically active individuals.