The aim of the study was to develop and validate a short questionnaire assessing four dimensions of impulsivity (urgency, lack of premeditation, lack of perseverance, sensation seeking) in patients with traumatic brain injury (TBI). To this end, 82 patients with TBI and their caregivers completed a short questionnaire adapted from the UPPS Impulsive Behavior Scale designed to assess impulsivity changes after TBI. Confirmatory factor analyses (CFAs) performed on the version of the scale completed by the relatives revealed that a hierarchical model holding that lack of premeditation and lack of perseverance are facets of a higher order construct (lack of conscientiousness), with urgency and sensation seeking as separate correlated factors, fit the data best. Urgency, lack of premeditation, and lack of perseverance increased after the TBI, whereas sensation seeking decreased. CFA failed to reveal a satisfactory model in the version of the scale completed by the patients. The psychological processes related to these impulsivity changes and the discrepancy observed between self-report and informant-report are discussed. This short questionnaire opens up interesting prospects for better comprehension and assessment of behavioural symptoms of TBI.