Because of their dynamic environments, today’s organizations cannot anticipate on or specify all desired employee behaviors. Therefore, many organizations need their employees to engage in extra-role performance by taking on extra tasks and responsibilities and come up with creative solutions for problems. Extra-role performance is not formally rewarded but performed for self-generated, intrinsic reasons (Piccolo and Colquitt, 2006). Intrinsic motivation, doing an activity for the satisfaction that it gives rather than for its instrumentality in achieving rewards (Gagné and Deci, 2005), has been consistently found to predict extra-role performance (Cerasoli et al., 2014). However, intrinsic motivation does not come naturally: according to a Gallup employee survey in 142 countries the majority of employees worldwide (63 percent) lack motivation and are less likely to invest discretionary effort in organizational goals or outcomes (Crabtree, 2013). One way to motivate employees to engage in extra-role performance is via great leaders who make work more intrinsically motivating (Piccolo and Colquitt, 2006). Transformational leaders have consistently been shown to motivate employees to engage in extra-role performance (Wang et al., 2011), because they are able to create a resourceful work environment that contributes to employees’ intrinsic motivation (Piccolo and Colquitt, 2006). By being supportive, allowing followers to decide for themselves how to perform their tasks, and taking into account their individual needs and abilities when delegating tasks, transformational leaders fulfill their followers’ basic needs for autonomy, competence, and relatedness (Deci and Ryan, 2000), leading to intrinsic motivation (Breevaart et al., 2014). However, the same dynamical context that demands for extra-role performance results in ongoing changes in management structures, leaving many subordinates uncertain about the availability of a transformational leader to motivate them (Zhao et al., 2016). In such contexts, a psychological resource such as mindfulness may make up for the low levels of transformational leadership in maintaining positive attitudes and performance (Manz and Sims, 1980; Nübold et al., 2013). Although the literature on positive organizational behavior and psychological capital has mainly focused on optimism, hope, resiliency, and self-efficacy as malleable human capacities that are associated with resiliency and self-management (Avey et al., 2011; Luthans, 2002), it has also been suggested that there may be more psychological resources that are in need of discovering (Luthans et al., 2007). We argue that mindfulness may be such a resource, because mindful individuals are more aware of their present experiences and are better able to regulate their behavior in line with their intrinsic needs (Rynes et al., 2007), which facilitates their intrinsic motivation (Gagné and Deci, 2005). The main contribution of our paper not lies in providing evidence for the mechanism by which transformational leadership leads to extra-role performance, because this relationship has been well evidenced (Wang et al., 2011; Den Hartog and Belschak, 2012; Piccolo and Colquitt, 2006). However, our main aim is to contribute to the still scarce research on interactions between leadership behavior and follower characteristics that predict the motivation and behavior of employees (Nübold et al., 2013). Our paper builds on the “substitutes for leadership” theory (Kerr and Jermier, 1978; Podsakoffet al., 1996), which posits that job, organization and worker characteristics may moderate the leader’s ability to affect employee attitudes, behaviors, and performance. Because mindful employees are better able to regulate their motivation and behavior (Brown and Ryan, 2003), they are better self-leaders (Houghton and Neck, 2002), thereby potentially reducing the need for external leadership (Manz and Sims, 1980). By pinpointing intrinsic motivation as the crucial mechanism by which both transformational leadership and mindfulness contribute to positive employee behavior such as extra-role performance, we aim to investigate the extent to which mindfulness is another form of psychological capital that may compensate for transformational leadership in achieving intrinsic motivation and extra-role performance. Our paper builds on positive organization behavior, which puts emphasis on human resource strengths and psychological capacities that are relatively malleable and can be developed to thrive at work (Luthans, 2002). Since mindfulness can be trained and improved (Brown and Ryan, 2003) it qualifies as an additional psychological resource capacity besides hope, optimism, and resilience (Malinowski and Lim, 2015; Youssef and Luthans, 2007). In addition, our paper contributes to the literature on mindfulness which until recently has neglected its work-specific outcomes (Dane, 2011; Hülsheger et al., 2013; Leroy et al., 2013), by not only addressing the question whether mindfulness works, but also providing insight into the mechanisms through which mindfulness works, thereby answering to the call of Shapiro et al. (2006).