Background The Quality of Life after Brain Injury (QOLIBRI) scale is a recently developed instrument that provides a profile of health-related quality of life (HRQoL) in domains typically affected by brain injury. However, for global assessment it is desirable to have a brief summary measure. This study examined a 6-item QOLIBRI Overall Scale (QOLIBRI-OS), and considered whether it could provide an index of HRQoL after traumatic brain injury (TBI). Methods The properties of the QOLIBRI-OS were studied in a sample of 792 participants with TBI recruited from centres in nine countries covering six languages. An examination of construct validity was undertaken on a subsample of 153 participants recruited in Germany who had been assessed on two relevant brief quality of life measures, the Satisfaction With Life Scale and the Quality of Life Visual Analogue Scale. Results The reliability of the QOLIBRI-OS was good (Cronbach's a 0.86, test-retest reliability =0.81) and similar in participants with higher and lower cognitive performance. Factor analysis indicated that the scale is unidimensional. Rasch analysis also showed a satisfactory fit with this model. The QOLIBRI-OS correlates highly with the total score from the full QOLIBRI scale (r=0.87). Moderate to strong relationships were found among the QOLIBRI-OS and the Extended Glasgow Outcome Scale, Short-Form-36, and Hospital Anxiety and Depression scale (r=0.54 to -0.76). The QOLIBRI-OS showed good construct validity in the TBI group. Conclusions The QOLIBRI-OS assesses a similar construct to the QOLIBRI total score and can be used as a brief index of HRQoL for TBI.