INTRODUCTION: Anxiety symptoms are commonly endorsed by student athletes. This study examined the possible influence of anxiety on baseline cognitive testing and symptom reporting in a large sample of adolescent student athletes. METHODS: Participants were 37,945 adolescent student athletes from the state of Maine who completed baseline testing using ImPACT(R). ImPACT(R) includes an evaluation of cognitive functioning and a questionnaire assessing the presence and severity of common post-concussion symptoms. Participants were divided into high and low anxiety groups based on endorsement of anxiety-like symptoms. RESULTS: Student athletes in the high anxiety group were more likely to be girls and to have a greater lifetime history of treatment for mental health problems and headaches (ps<.001). The high anxiety group scored slightly lower on cognitive tests (Cohen's ds=0.15-0.26) and reported a much greater amount of baseline preseason symptoms (Cohen's d=3.38). More than eight out of ten youth in the high anxiety group (82.7%) met International Statistical Classification of Diseases and Related Health Problems-10th Revision (ICD-10) symptom criteria for at least a mild form of the postconcussional syndrome compared to less than two out of ten (18.4%) in the low anxiety group. CONCLUSION: Students in the high anxiety group had slightly lower scores on neurocognitive testing, but the differences were not practically meaningful; however, they endorsed dramatically more physical, cognitive, and emotional symptoms. Anxiety can mimic the ICD-10 postconcussional syndrome in adolescent student athletes at baseline, when they have not been injured.