The definition of mild traumatic brain injury (TBI) published by the American Congress of Rehabilitation Medicine (ACRM) in 1993 has guided clinical practice and research over the past 25 years. In 2019, the Mild TBI Task Force of the ACRM Brain Injury Special Interest Group undertook updating the definition and diagnostic criteria for mild TBI. This work included rapid evidence reviews, an expert survey (to rate the diagnostic importance of various clinical signs, symptoms, test findings, and contextual factors), public and stakeholder engagement, and a Delphi consensus process with an international, interdisciplinary panel of clinician scientists. The new diagnostic criteria were published in the summer of 2023. This presentation will provide an overview of these activities and then present the new consensus diagnostic criteria for mild TBI. Case examples will be presented to illustrate how the diagnostic criteria can be applied.