While the evidence on the adverse impact of the COVID-19 pandemic on the well-being of frontline social workers is emerging, the research on the impact of the pandemic on their performance is scarce. The presented study explores how the relationship between work environment predictors and perceived stress explains the job performance of child welfare social workers during the pandemic using survey responses of 878 child welfare social workers. The findings revealed the mechanism through which environment predictors and perceived stress interacted in explaining job performance during a time of large-scale crisis. We found that C.W. social workers who experienced greater COVID-19-related service restrictions reported poorer job performance, that perceived stress disrupted workers’ supervision and autonomy, and that supervision and job autonomy protected C.W. social workers from the adverse effects of perceived stress and workload on their job performance. Conclusions included the importance of autonomy and supervision in mitigating job-related stressors and the need to adapt and enhance child welfare supervision during times of national crisis.