The growing mental health crisis in contemporary workplaces necessitates systemic, preventive, and relationally grounded interventions that move beyond individual coping strategies. While existing organisational approaches largely emphasise resilience training and stress management, comparatively little empirical attention has been devoted to peace-oriented competencies as structural determinants of workplace well-being. This study develops and tests a Peace-Oriented Workplace Well-Being Model that conceptualises peace competencies—empathy, emotional regulation, non-violent communication, tolerance, and collaborative conflict transformation—as foundational predictors of psychological safety and mental well-being, culminating in organisational thriving. Using a convergent mixed-methods design, data were collected from 200 employees across four sectors. Quantitative analyses included reliability assessment, correlation analysis, hierarchical regression, and bootstrapped mediation testing. Results revealed significant positive associations between peace competencies and psychological safety (r = .68, p < .001) and between peace competencies and mental well-being (r = .62, p < .001). Mediation analysis indicated a significant indirect effect through psychological safety (indirect effect = .27, 95% CI [.18, .38]), confirming partial mediation. Qualitative thematic findings provided contextual depth, illustrating how relational climates characterised by respectful dialogue and constructive conflict engagement function as psychosocial buffers. Building on these findings, the study proposes a multi-level Peace-Oriented Policy and Practice Framework integrating individual competency development, team-based relational systems, leadership accountability, and organisational governance architecture. The research positions peace not as a normative ideal but as measurable preventive infrastructure for sustainable workplace mental health and thriving.