Disclosed are methods and compositions for treating traumatic brain injury (TBI). A brain injury-specific 4-amino acid peptide (sequence CAQK), identified by in vivo phage display screening in mice with acute brain injury, shows selective binding to mouse and human brain injury lesions, and when systemically injected, specifically homes to sites of injury in penetrating and non-penetrating (controlled cortical impact) brain injury models. Significantly, the peptide alone produces therapeutic effect and so can be used in the absence of any other therapeutic compound.