Purpose Mobbing is a serious problem with major consequences for workers’ health and company productivity. This study aims to examine the impact of workplace mobbing on the mental well-being of employees, with a specific focus on knowledge hiding and quiet quitting as sequential mediators. Using social exchange theory (SET), this study aims to clarify the consequences of toxic workplace environments, both in terms of knowledge-related actions and employee psychological states, in a hospitality setting. Design/methodology/approach The authors conduct two studies, taking a quantitative approach to generalize the findings. Study 1 is conducted in a hospitality setting, focusing on employees (n = 298), and Study 2 is a survey of general working staff (n = 183). In both cases, partial least squares structural equation modeling (PLS-SEM) is used to analyse the direct and indirect relationships among the variables. Findings The findings indicate that workplace mobbing significantly affects knowledge hiding and quiet quitting behaviours. In addition, knowledge hiding significantly mediates the relationship between workplace mobbing and quiet quitting, further mediating the relationship between knowledge hiding and employee mental well-being. These findings highlight the cascading effect of mobbing on knowledge management dynamics as well as the mental health of employees. Research limitations/implications The evidence extracted from the findings underscores the necessity for targeted interventions that prevent workplace mobbing and discourage knowledge hiding and quiet quitting behaviours. Organizations, especially service-oriented firms, should promote knowledge exchange behaviour based on a culture established on trust. Originality/value This study makes a significant contribution to the field of knowledge management by revealing the sequential pathway that connects workplace mobbing with mental well-being through knowledge hiding and quiet quitting. It highlights the detrimental impact of toxic social interactions on employee mental health and organizational knowledge flows.