OBJECTIVES: As part of the "Japan Environment and Children's Study (JECS)," a national prospective birth cohort study, we examined the association between the maternal work environment and psychological distress during pregnancy in Japan. METHODS: Employing a cross-sectional design, we analyzed data from 42,797 participants, originally collected between 2011 and 2014. Associations between the maternal work environment and psychological distress (Kessler 6) were examined using generalized estimation equation models adjusted for confounding factors. RESULTS: Pregnant women who worked ≥51 hours/week had a 1.19-fold higher odds ratio (OR) of psychological distress than those who worked 36 to 40 hours/week (95% confidence intervals [CIs], 1.07-1.32). Pregnant women who worked ≥5 days/month of shift work had a 1.11-fold higher OR of psychological distress than those who worked 0 days/month (1.00-1.24). CONCLUSIONS: We observed an association between the maternal work environment and psychological distress during pregnancy.