Employee well-being has become a strategic imperative as organizations worldwide confront rising burnout, disengagement, and the human costs of intensified competition. Yet organizations face a paradox: the high-performance work systems (HPWS) they adopt to remain competitive may either nourish or erode the well-being of the employees who enact them. Motivated by this tension, this study investigates not only whether HPWS influences employees’ subjective well-being (SWB), but also how and when this influence occurs. Drawing on self-determination theory, it proposes that HPWS enhances SWB by satisfying employees’ basic psychological needs for autonomy, competence, and relatedness, thereby strengthening their emotional commitment to the organization, and that interpersonal fairness – the need-supportive quality of day-to-day interpersonal treatment – conditions this process. Three-wave, multi-source data were collected from 412 employees across 68 teams in Chinese technology companies, and the hypothesized moderated mediation model was tested using hierarchical linear modeling and bootstrap methods. The results revealed that: (1) HPWS positively influences employees’ SWB; (2) emotional commitment partially mediates this relationship; (3) interpersonal fairness moderates the HPWS-emotional commitment link, such that the positive effect is stronger when interpersonal fairness is high; and (4) the indirect effect of HPWS on SWB through emotional commitment is likewise stronger when interpersonal fairness is high. These findings extend self-determination theory into the strategic human resource management domain by identifying emotional commitment as a need-based transmission mechanism and interpersonal fairness as a need-supportive boundary condition, and they offer actionable guidance for designing HPWS that pursue performance goals without sacrificing employee well-being. By responding to recent calls for mechanism-focused and context-sensitive HRM-well-being research, the study shows how performance systems can be designed to serve both organizational and employee interests.