Unethical pro-supervisor behavior (UPSB), a topic which has drawn increasing attention from the organizational behavior field in recent years, refers to unethical acts conducted by subordinates to benefit supervisors. UPSB is prevalent in organizations, especially the Chinese organization which is characterized as guanxi-oriented and authority-oriented. UPSB serves supervisors’ interests, sometimes at the expense of the organization. Therefore, it is imperative to explore the antecedents of UPSB and their influencing mechanisms, so as to provide the organization with suggestions of how to control such behavior. Regrettably, studies on UPSB are rather limited, let alone the ones based on the Chinese context. Given this, the present study is to take root in the Chinese cultural context and explore the influencing mechanism of supervisor-subordinate guanxi (SSG), subordinate traditionality, and enterprise property on UPSB.Data were collected from 14 indigenous enterprises in Yangtze River Delta, China, including 8 state-owned enterprises and 6 private enterprises. To reduce the interference of common method bias, we carried out a two-phase questionnaire survey with one month interval. At the first phase, participants reported their SSG, traditionality, and related control variables. At the second phase, participants reported their UPSB. The final valid sample consisted of 327 employees from 49 teams. Using SPSS 26.0 and Mplus 8.3, we conducted confirmatory factor analysis, correlation analysis, and hierarchical linear modeling analysis to generate results.The empirical results show that SSG has a U-shaped relationship with UPSB, that is, as the levels of SSG increase from moderate to high, employees’ UPSB increases; as the levels of SSG decrease from moderate to low, employees’ UPSB also increases. Moreover, we find that this U-shaped relationship is more pronounced among subordinates higher in traditionality, and SSG has a stronger U-shaped impact on UPSB in state-owned enterprises. These two findings provide evidence that traditionality and enterprise property are important boundary conditions of the curvilinear relationship between SSG and UPSB.This study has two theoretical contributions: First, based on the Chinese cultural context, it proposes and examines the U-shaped impact of SSG on UPSB, thereby not only deepening the current understanding of how UPSB occurs through the lens of social exchange theory, but also enriching the research on the outcomes of SSG. Second, based on the contingent view of social exchange and person-situation interactionist view of ethical decision-making, we demonstrate the moderating roles of subordinate traditionality and enterprise property on the impact of SSG on UPSB, thus not only revealing the boundary conditions of the relationship between SSG and UPSB, but also responding to the call for conducting highly-indigenous research.