This study develops a theoretical model that explains how leaders come to adapt their leadership behaviors to achieve follower effectiveness. Mindfulness theory suggests that mindful individuals are better able to engage in self-regulation and I consider empathy, response flexibility, and emotional regulation as three self-regulatory processes in particular which likely impact the leader-follower relationship. I suggest that leaders who have the ability to self-regulate in these three ways will be better able to engage in leadership behavior characterized by adapting or flexing the specific types of leadership they demonstrate according to the needs of the situation and what their followers most require at a given time to perform at their best. When followers receive the type of situationally-appropriate support in the form of leader behavior, they are more effective (e.g. have higher job performance and extra-role performance). I validate a new trait and state measure of workplace mindfulness with multiple samples and utilize this new scale to collect data from leaders and followers from a government organization to test the theoretical relationships proposed in this study. I utilize an experience sampling methodology (ESM) design over 10 days to investigate the within-leader variation among variables in the study given theory suggesting the dynamic nature of the mindfulness, self-regulation, and situational leadership constructs which may not adequately be captured when data are collected at one point in time. Finally, I introduce organizational constraints as a moderator of the relationship between leader mindfulness and leader self- regulation in order to understand how stressors and strains outside the control of a leader may overload a leader’s ability to ultimately self-regulate his/her behavior.