Scant research has examined health-related quality of life (HRQoL) in family members of patients with severe brain injury, even less has been done in Scandinavian countries, and none has examined this construct longitudinally. The current study therefore used multilevel modelling to investigate the trajectories of HRQoL in 94 Danish family members of patients with severe brain injury at five time points, beginning at the patient's stay in a neuro intensive care unit through one year after injury. The family members’ HRQoL scores significantly and strongly increased over time, and Role Limitations – Emotional scores were higher when patients had high Rancho Los Amigos Scale scores at admission to early intensive rehabilitation in hospital. These results suggest that the acute and sub-acute periods after brain injury are an extremely difficult time psychologically for many families, and family-based mental health interventions during the acute and sub-acute phases are critical, especially for families who have a patient with severe deficits.