Objective: Mental health professionals are often exposed to workplace violence (WPV) in China. This study examined the prevalence of WPV and the associated factors and quality of life (QOL) among frontline mental health professionals during the COVID-19 pandemic. Methods: This national survey was carried out between March 15 and March 20, 2020. WPV and QOL were assessed with standardized measures. Results: A total of 10,516 participants were included. The prevalence of overall WPV was 18.5% (95% CI: 17.9%–19.3%), while verbal abuse/threats was 15.8% and physical violence was 8.4%. Multiple logistic regression analysis revealed that male gender (OR = 1.42, p < 0.01), higher educational level (OR = 1.40, p < 0.01), working in tertiary hospitals (OR = 1.33, p < 0.01), caring for COVID-19 patients (OR = 3.10, p < 0.01) and having more severe anxiety symptom (OR = 1.21, p < 0.01) were positively associated with WPV. In contrast, working in inpatient departments (OR = 0.74, p < 0.01), having longer work experience (OR = 0.99, p = 0.03), and being a junior nurse (OR = 0.73, p < 0.01) were negatively associated with WPV. After controlling for the covariates, mental health professionals who experienced WPV had a lower overall QOL compared to those without WPV (F = 68.28, p < 0.01). Conclusion: This study found that WPV was common among mental health professionals in China during the COVID-19 pandemic. Considering the negative impact of WPV on QOL and quality of patient care, appropriate measures to prevent WPV should be developed.