Traumatic brain injury (TBI) often results in long-term cognitive impairments. This is often due to the disruption of brain networks that support cognition. Major advances have recently been made in our understanding of these networks. Here we review work that investigates the effect of TBI on brain networks, and discuss the potential importance of these findings for rehabilitation. Large-scale brain networks, which we refer to as intrinsic connectivity networks (ICNs), have been identified. Traumatic axonal injury disrupts their white-matter connections, and altered brain activity within the networks is frequently observed after TBI. These changes relate to the pattern of cognitive impairment, and are useful for predicting clinical outcome. The effect of drugs such as methylphenidate, which can be used to augment rehabilitation, are beginning to be studied in the context of their effect on network function after TBI. The assessment of brain network function after TBI provides insights into the pathophysiology of cognitive dysfunction and the mechanisms involved in recovery. These advances should provide the basis for a more detailed understanding of rehabilitation, and ultimately guide the development of targeted individualized therapy after TBI.