<p id="p00005">Currently, workaholic leaders are prevalent in the workplace, and the relevant research has substantially increased. However, regarding the effectiveness of leader workaholism, researchers have found inconsistent and even contradictory results. In addition, prior research has mostly centered on the effects of leader workaholism at the employee or firm level while ignoring its impacts at the team level. To address these gaps, the current research aims to investigate the double-edged sword effects of leader workaholism on team performance. Based on social information processing theory, we propose that leader workaholism influences team performance through two distinct mechanisms: on the one hand, leader workaholism enhances team job involvement, which has a subsequent positive effect on team performance, and on the other hand, leader workaholism induces team negative affect, which in turn negatively influences team performance. In addition, we also expect that team task significance can mitigate the negative effects and enhance the positive effects of leader workaholism. <p id="p00010">We conducted a multitime, multisource questionnaire survey on a property management company in China. Before collecting the data, all participants were assured that their responses would be confidential and used only for academic research. In Wave 1, the team leader rated his or her workaholism, and team members rated team task significance. In Wave 2 (one month later), team members were asked to complete the questionnaire containing questions on team job involvement and team negative affect. In Wave 3 (one month after Wave 2), general managers were invited to evaluate each team’s performance. The three rounds of data collection resulted in 105 matched team leader-team member responses (105 team leaders, 512 team members), with a 69.08% overall response rate for team leaders and a 61.03% overall response rate for team members. <p id="p00015">Before testing the hypotheses, we conducted a measurement model assessment to verify whether the manifest variables could accurately measure the theoretical constructs. Then, we performed a path analysis through Mplus 7.0. The results showed that leader workaholism was positively related to team job involvement, resulting in higher team performance. However, leader workaholism also heightened team negative affect, thus decreasing team performance. Moreover, team task significance moderated the above two mediating paths. Specifically, when team task significance was higher, the negative mediating effect of team negative affect was attenuated, and the positive mediating effect of team job involvement was enhanced. <p id="p00020">The current research makes essential theoretical contributions and has practical implications. First, this study is among the first to examine the relationship between leader workaholism and team performance, answering the call for more research on the effects of leader workaholism at the team level (Clark et al., <xref xml:base="bibr" rid="b6">2016</xref>). Second, based on social information processing theory, we examine two mechanisms through which leader workaholism affects team performance and demonstrate the coexistence of opposite effects in this process, which is helpful for understanding the complicated relationship between leader workaholism and team performance. Third, we elaborate on the moderating role of team task significance, which provides important insights about the contingency factors that shape the effectiveness of leader workaholism. Practically, we suggest that organizations take a dialectical perspective to consider the role of leader workaholism in team management and adopt selection procedures to identify qualified managers.