Core self-evaluation (CSE) is malleable. However, little is known about leadership qualities for facilitating CSE. This study investigated the mediating role of psychological well-being (PWB) on the relationship between transformational leadership and CSE with supervisor-subordinate guanxi (SSG) or non-work social relationship qualities. A convenience sample of 406 employees (54.2% = female; mean age = 34.81 years, SD = 7.6 years) responded to questionnaires on demographic variables, transformational leadership, SSG, PWB, and CSE. Multiple regression and bootstrapping analyses showed transformational leadership to enhance both CSE and PWB. Further, PWB mediated the effect of transformational leadership on CSE. In addition, SSG positively moderated the direct effect of transformational leadership on PWB. SSG also positively moderated the indirect effect of transformational leadership on CSE via PWB. Our findings suggest transformational leadership and SSG are resources for employee well-being.