Prospective memory (PM), the ability to recall future intentions, is crucial for independent living. Impairment of PM is a common complaint following head injury and is a significant impediment to good recovery, yet no studies have explored PM in mild traumatic brain injury (mTBI). In this study, prospective memory was examined in 31 mTBI patients and matched controls within a month of injury and 3 months after. mTBI patients performed more poorly than controls on the MIST task (Raskin, 2004) within the first month following injury, indicating that PM impairment is part of the acute cognitive sequelae of mTBI. These problems persisted beyond 3 months post-injury, suggesting that PM may be a sensitive indicator of cerebral compromise in mild brain injuries.