Abstract This study investigates the effect of workplace harassment on work quality in six tertiary healthcare facilities in South-West, Nigeria. Drawing upon Conservation of Resources (COR) theory propounded by Dr. Stevan E. Hobfoll in 1989, in the area of stress and motivation research, the main thrust of the theory lies on how organisation strives to acquire, maintain, and protect their resources in order to manage stress and promote well-being. This study offers a useful framework for analyzing the effects of workplace harassment on the work quality of health workers. This study adopted survey research design. The population was 6,359 health workers from six teaching hospitals in South-West, Nigeria. The sample size of 475 was determined using Krejcie and Morgan table. Purposive sampling technique was adopted to select the respondents. A structured and validated questionnaire was used for data collection. Response rate was 100%. Cronbach’s alpha reliability coefficient for the constructs ranged from 0.71 and 0.94. Data were analysed using inferential (multiple linear and hierarchical regression) statistics at 5% significance level. The findings revealed that workplace harassment have significant effect on work quality of the selected tertiary hospitals in South-West, Nigeria (Adj.R2= 0.101, F(5, 475) =11.668, p<0.05). The findings highlight the role of workplace harassment dimensions: Abusive supervision, workplace incivility, workplace ostracism, verbal aggression and workplace violence on employee work quality. The results of the analysis revealed that workplace harassment have positive and significant effect on work quality of the selected tertiary hospitals in South-West, Nigeria. This indicates that workplace ostracism, abusive supervision in the workplace, workplace incivility and workplace verbal aggressions were important predictors of work quality of the selected tertiary hospitals in South-West, Nigeria. The study recommended that management should develop and enforce clear anti-harassment policies that outline unacceptable behaviors and the consequences of such actions, and ensure that these policies are communicated effectively to all employees at all levels of management. KEYWORDS: Workplace harassment, Abusive supervision, workplace incivility, workplace ostracism, verbal aggression, workplace violence, work quality