<p>In the current organizational context, it has become far more prevalent for employees to engage in multiple teams simultaneously. Drawing on the Job Demands-Resources (JD-R) model and Conservation of Resources (COR) theory, we examine the “double-edged sword” effect of multiple team membership (MTM) on employees’ job performance, with thriving at work and job burnout serving as mediators, and organizational tenure acting as a moderator. By analyzing the time- lagged survey data collected from 214 employees, empirical results indicate that MTM can positively affect job performance by promoting employees’ thriving at work. However, it can also negatively influence job performance by triggering job burnout. Additionally, organizational tenure significantly strengthens the positive influence of MTM on employees’ thriving at work, further strengthening its positive effect on job performance via thriving at work. At the same time, organizational tenure also moderates the negative impact of MTM on job burnout. These empirical findings provide important insights into the intricate effect of MTM and have practical implications for team leaders to effectively manage MTM in organizational environments.</p>