Transformational leadership, generally considered as a desirable leadership style, has positive effects on various performance outcomes of employees; however, its productivity has been called into question because of a relative neglect of its negative aspects. Addressing this gap, an attempt at rethinking the relationship between transformational leadership and employee performance is important. The paradoxical perspective indicates that conflicting positive and negative effects of transformational leadership can coexist, which provides possibility and rationality for thorough consideration of employees' task performance influenced by transformational leaders. Integrating the principle of diminishing marginal utility and the "Too-Much-ofa-Good-Thing (TMGT)" effect, this research explores an inverted U-shaped relationship between transformational leadership and employee task performance. Furthermore, applying social cognitive theory, we assume an employee's proactive personality moderates the curvilinear influence of transformational leadership on employees' task performance. As expected, results from a study of data from 209 supervisorsubordinate relationships from China showed that the inverted U-shaped relationship between transformational leadership and employees' task performance was moderated by employees' proactive personality. Theoretical and practical implications are discussed.