Patients with severe traumatic brain injury (TBI) frequently suffer from a difficulty in dealing with two tasks simultaneously. However, there has been little research on the rehabilitation of divided attention. The objective of the present study was to assess the effectiveness of a rehabilitation programme for divided attention after severe TBI. Twelve patients at a subacute/chronic stage after a severe TBI were included. A randomised AB vs. BA cross-over design was used. Training lasted six weeks, with four one-hour sessions per week. It was compared to a non-specific (control) cognitive training. During experimental treatment, patients were trained to perform two concurrent tasks simultaneously. Each one of the two tasks was first trained as a single task, then both tasks were given simultaneously. A progressive hierarchical order of difficulty was used, by progressively increasing task difficulty following each patient's individual improvement. Patients were randomised in two groups: one starting with dual-task training, the other with control training. Outcome measures included target dual-task measures, executive and working memory tasks, non-target tasks, and the Rating Scale of Attentional Behaviour addressing attentional problems in everyday life. Assessment was not blind to treatment condition. A significant training-related effect was found on dual-task measures and on the divided attention item of the Rating Scale of Attentional Behaviour. There was only little effect on executive measures, and no significant effect on non-target measures. These results suggest that training had specific effects on divided attention and helped patients to deal more rapidly and more accurately with dual-task situations.