Second only to a clinical exam, symptom checklists are used to aid in the evaluation of concussions. The validity of symptom checklists can become compromised by nonconcussed linked conditions that can vary day to day and are not taken into consideration during a baseline test. The purpose of this study was to assess the day-to-day reliability of the SCAT3 Symptom Evaluation and to determine the frequency and severity of the 22 symptoms in a nonconcussed, adult, athletic population. This study used a repeated-measure observational design and required participants to complete an online version of the SCAT3 Symptom Evaluation multiple times over a 7-day period. Moderate day-to-day reliability was found for the frequency and severity of symptoms and all of the 22 symptoms were reported by at least one participant. The results of the study suggest that the current practice of collecting the baseline symptoms once does not account for any day-to-day variation in symptoms and also demonstrates that all of the 22 symptoms listed on the SCAT3 Symptom Checklist can be present in nonconcussed, adult athletes.