Concrete behaviour, the inability to disengage from immediate experience in order to manipulate ideas and thoughts, has long been understood to be a common problem after frontal lobe lesions. However, there has been little consideration of the impact that concreteness may have on emotional functioning, specifically in the use of thinking to manipulate emotional responses. One widely studied emotion regulation strategy is reappraisal, which depends on several frontal lobe related cognitive control processes. While there have been numerous neuroimaging findings on reappraisal, no study has used brain injured patients to investigate this issue. The present case study is the first to describe the capacity to generate reappraisals in a patient (Mrs M), whose behaviour became concrete after a left prefrontal stroke. Using a picture-based reappraisal paradigm, her performance was compared to non-concrete brain-lesioned patients, and neurologically healthy controls. Although Mrs M showed relatively preserved overall cognitive function, she was completely unable to spontaneously generate reappraisals. In striking contrast, once external support was offered, in the form of prompts, her capacity to reappraise dramatically improved. The results are analysed in terms of three neuropsychological capacities - all compromised in Mrs M - previously proposed as reappraisal components: response inhibition, abstraction, and verbal fluency. A number of implications for rehabilitation are discussed, including how the use of prompting may facilitate reappraisal capacity.