Despite popular opinion that passion is a necessary ingredient for leadership, scholars have little insight into how, when, or even if leader passion impacts follower outcomes. I therefore make several contributions towards increasing scholarly understanding in this area. First, I reviewed existing definitions and measures of passion relevant to the workplace and provided a new, more comprehensive definition of work passion that conceptually differentiates it from related constructs. I also used socioanalytic theory to distinguish between felt work passion, which contains affective and cognitive elements, and displayed work passion, which contains behavioral elements. Second, in order to better align theory and measurement, I developed and validated new measures of felt (self-report) and displayed (other-report) work passion in two samples of working adults. The scales showed good convergent validity with other measures of work-related passion, somewhat concerning discriminant validity with job attitudes such as engagement and job satisfaction, and evidence of criterion validity with leader-member exchange. Third, I integrated social cognitive theory with theories of emotion, motive, and goal contagion to conduct an initial test of a multilevel moderated mediation model of how leader felt and displayed work passion influence follower felt work passion and performance, contingent on the emotional intelligence of both leaders and followers. In a sample of leaders and followers employed by a staffing agency, although I did not find support for my hypotheses, analysis suggested that leader displayed passion may interact with follower characteristics to predict follower outcomes.