Two experiments tested the hypothesis that exposure to masked emotional expressions during the performance of cognitive tasks influences effort mobilization. In support of the predictions, participants who processed masked sad faces during task performance under “do your best” instructions showed stronger sympathetic nervous system discharge to the heart (shorter pre-ejection period, higher systolic blood pressure) than participants who were exposed to masked smiling faces or angry faces. Assessed task appraisals suggest that these effects on effort-related cardiovascular reactivity occurred because the masked emotional stimuli influenced the level of experienced task difficulty. The findings are compatible with the effects of consciously experienced affect on effort-related cardiovascular response.