Background: Assessing sport-related concussions in athletes presents challenges due to symptom variability. This study aimed to explore the relationship between acute concussion symptoms and athlete fear avoidance, pain catastrophizing, depression, and anxiety. Anxiety and depression have previously been associated with the number of symptoms after a concussion, but no prior research has examined the possible link between athlete fear avoidance and acute concussion symptoms. Methods: Thirty-four collegiate athletes (mean age = 20.9 ± 1.8 years) were assessed within 48 h of a concussion using the Sport Concussion Assessment Tool 5, Athlete Fear Avoidance Questionnaire (AFAQ), Pain Catastrophizing Scale, and Hospital Anxiety and Depression Scale. Results: Results showed a significant association between the athlete fear avoidance and the number of concussion symptoms (r = 0.493, p = 0.003), as well as depression and anxiety measured by HADS (r = 0.686, p < 0.001). Athlete fear avoidance and HADS scores were predictors of symptom severity, explaining 41% of the variance (p = 0.001). Athletes with higher fear avoidance tended to report more symptoms post concussion. Conclusions: This study underscores the link between athlete fear avoidance, anxiety, depression, and the severity of concussion symptoms. Administering the AFAQ to assess athlete fear avoidance at the initial assessment of a concussion may be helpful in interpreting the symptoms of an acute concussion.