The Sport Concussion Assessment Tool 5 (SCAT5) is a standardized tool for evaluating suspected sport-related concussions in athletes aged 13 and older (Child-SCAT5 for ages 5-12). Concussion is a traumatic brain injury induced by biomechanical forces causing a complex pathophysiological process: rotational acceleration-deceleration forces stretch and shear axons, causing a neurometabolic cascade. This cascade includes: ionic imbalance (potassium efflux, calcium influx), glutamate release and excitotoxicity, mitochondrial dysfunction, impaired cerebral blood flow autoregulation, and energy crisis as ATP demands for ionic rebalancing exceed supply. The SCAT5 includes multiple components: immediate assessment (red flags, observable signs, GCS, cervical spine assessment), symptom evaluation (22-symptom checklist with severity scale), cognitive screening (orientation, immediate memory, concentration), neurological screening (balance testing using modified Balance Error Scoring System — mBESS), and delayed recall. A baseline SCAT5 performed preseason allows comparison with post-injury assessment. Key principle: when in doubt, sit them out. No athlete diagnosed with concussion should return to sport on the same day. Return-to-sport requires a graded protocol with minimum 24 hours between each step.