The COVID-19 pandemic has led to significant changes in work and lifestyle, impacting occupational mental health. This study examines the time and individual heterogeneity in the pandemic's effects on occupational mental health using panel data from job stress checks spanning 2018 to 2021. On average, there was an initial alleviation of high-stress risk in 2020, followed by a deterioration in 2021. Based on the job demand-resource theory, we identify the group of employees most affected by the pandemic. The findings highlight that employees in unfavorable workplace conditions are more likely to experience substantial adverse impacts. Adequate workplace support, including factors like interpersonal relationships, managerial support, job meaning, control, and work-life balance, is crucial for mitigating high-stress risk. Additionally, during the early phase of the pandemic, engaged employees experienced a slight decline in occupational mental health, while those lacking job resources at their worksite faced higher levels of occupational stress in the subsequent year. These findings offer practical suggestions for person-centered coping strategies to mitigate the pandemic's adverse impact.