<p>While mindfulness training is often endorsed in workplaces due to its psychological and performance benefits, the mechanisms linking mindfulness to outcomes remain unclear. This study draws on social and psychological theories to explore whether psychological capital mediates the relationship between mindfulness and work engagement among hospitality employees, as well as how age and gender might moderate this association. Data collected from 203 hotel staff across two waves revealed that mindfulness was not directly associated with work engagement but exhibited an indirect relationship mediated by optimism. The strength of this indirect association differed across demographic groups: it was strongest among younger female employees, followed by middle-aged females, older females, younger males, and middle-aged males, with no significant link observed for older male employees. By clarifying the potential pathways and boundary conditions of the mindfulness–work engagement pathway, this study advances theoretical understanding and practical applications of mindfulness training within the hospitality sector.</p>