There has been substantial interest in emotion after acquired brain injury (ABI), but less attention paid to emotion regulation (ER). Research has focused primarily on the ER strategy of reappraisal for regulating negative emotions, without distinguishing between classes of emotion, and there has been no attempt at exploring these differences in patients with ABI. The present study explored components of reappraisal, across classes of emotion, and their associated neuropsychological mechanisms. Thirty-five patients with ABI and twenty-two matched healthy control participants (HCs) completed two questionnaires, a battery of cognitive tasks, and an emotion regulation task (the Affective Story Recall Reappraisal task). Results suggest that those with ABI take longer, and generate fewer reappraisals than HCs across several discrete emotions. Notably, their ability to decrease emotional intensity did not differ significantly to HCs for negative emotions, but findings suggest that their reappraisals are less effective when up-regulating neutral emotions to positive. Working memory was the only significant predictor of the total number of reappraisals generated, and the time taken to produce a first reappraisal. Implications of these findings are discussed in the context of neuropsychological rehabilitation, including the role of the relatives in implementing and reinforcing micro-interventions.