Drawing on the mood–behavior model (G. H. E. Gendolla, 2000) and J. W. Brehm and E. A. Self’s (1989) theory of effort mobilization, 2 experiments investigated the joint effect of mood, task difficulty, and performance-contingent consequences on effort-related cardiovascular response. Informational mood impact on demand appraisals and performance-contingent consequences had a joint effect on effort mobilization. When consequences were noncontingent on performance, mood interacted with task difficulty to determine cardiovascular reactivity in the shape of a cross-over interaction pattern. Yet when positive consequences were performance contingent, cardiovascular reactivity strongly increased only in the negative-mood/difficult-task condition—the subjectively appraised high necessary effort was now justified. Implications for the role of mood in motivation are discussed.