Medical social workers (MSWs) engage in complex and demanding work that inevitably affects their professional well-being. A public health disaster like coronavirus disease 2019 (COVID-19) exacerbates the effects. This study aims to classify the professional quality of life (ProQOL) of MSWs during COVID-19 in mainland China. It further examines the relationship between ProQOL classification, post-traumatic growth (PTG), and demographic characteristics. ProQOL comprises three domains: compassionate satisfaction, burnout and secondary traumatic stress. About 345 MSWs completed questionnaires that measured their levels of ProQOL and PTG. Through a k-mean cluster analysis, three clusters of ProQOL are identified. The first type is named as the Career Satisfied group, characterised by MSWs with the highest level of compassionate satisfaction and the lowest level of secondary traumatic stress and burnout amongst the three clusters. The second cluster is called the Trauma-Thriving group, consisting of MSWs with the highest level of secondary traumatic stress amongst all. They also had the highest score for PTG. The third cluster, the Compassion Fatigue group, comprised MSWs with the highest burnout and lowest compassion satisfaction levels. The results underscore the importance of tailored interventions for each type of MSW that emerges in a public health disaster.