Background: It has been suggested in the literature that raised heart rate in the early period after trauma is associated with the development of post-traumatic psychopathology, but little account has been taken of the potential confounding effect of injury severity. Materials and methods: A cohort of 154 patients, studied as part of a wider investigation of trauma outcomes, was included. Initial heart rate in the accident & emergency department, and injury severity score and new injury severity scores were recorded. Patients completed the General Health Questionnaire (GHQ-28) as a measure of psychopathology at presentation and again at two- and six-month follow-up. Results: There was no relationship between psychopathology at presentation and initial heart rate or injury severity. Raised heart rate was associated with post-traumatic psychopathology at two months but not at six months. When the potential confounding effect of injury severity was controlled for, there was no independent correlation between heart rate and post-traumatic psychopathology. Injury severity score and new injury severity scores were strongly associated with GHQ-28 caseness. Conclusion: Post-traumatic tachycardia is not associated with development of psychopathology, but injury severity is. Previous studies that have suggested a link between tachycardia and development of psychopathology are flawed because they have not considered the confounding effect of severity of injury.