Apathy is a decrease in behavioural, cognitive and emotional components of goal-directed behaviour. Clinically, it is characterised by diminished initiation, reduced concern, and decreased activity. Apathy is a common occurrence following traumatic brain injury (TBI), occurring in around 60% of people. Consequences are widespread, negatively impacting independence, social integration, rehabilitation outcome, vocational outcome, coping and caregiver burden. The current knowledge base on apathy following TBI is presented, with implications for clinical practice. This includes a review of clinical presentations, neuroanatomical and neurochemical substrates associated with apathy, and differential diagnoses. Instruments to measure apathy are presented, highlighting those with demonstrated reliability and validity for the TBI population. Current evidence for pharmacological and non-pharmacological methods of treatment is described, with a model for non-pharmacological interventions provided and discussion of challenges faced by clinicians when treating the patient with apathy. In the TBI arena, greater understanding of apathy and methods of treatment is pivotal given the frequency of occurrence and widespread negative consequences.