Context: Recent data suggest that females may be at a higher risk for sustaining concussive injuries, especially in soccer and basketball. Furthermore, some studies have identified that females may present differently with respect to symptoms and neurocognitive function following concussion. For clinicians, understanding sex differences in baseline concussion assessment measures is important for interpretation of post-injury scores. Objective: To investigate whether the factor structure of the graded symptom scale and individual symptom items differs between male and female adolescent athletes at baseline. Design: Cross-sectional. Setting: High school athletic training facilities. Patients or Other Participants: A convenience sample of 11,864 adolescent athletes (3912 females, 7952 males, age = 15.6 ± 1.2 years) participating in interscholastic contact sports. Intervention(s): All subjects completed the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT), as part of a concussion baseline assessment protocol. The independent variable was sex. Main Outcome Measure(s): Dependent variables included the 22-items of the graded symptom scale within ImPACT. Separate principal axis factor analyses with oblimin rotation and Kaiser normalization were conducted for each sex. Items were retained if loading factors were > 0.32. Separately, Mann-Whitney U tests were used to evaluate sex differences for each of the individual symptom items. Results: For males, a four-factor solution, consisting of 16 symptoms (Kaiser-Meyer-Olkin Measure = .93) was found: cognitive (28.2% of the variance) included: difficulty remembering, difficulty concentrating, balance problems, feeling slowed down, visual problems, foggy; emotional (4.3%) included: feeling emotional, sadness, nervousness; somatic (3.5%) included: nausea, vomiting, dizziness, headache; and sleep (2.0%) included: sleeping less, trouble falling asleep, fatigue. A four-factor structure, consisting of 21 items, was identified for females (Kaiser-Meyer-Olkin Measure = .93): cognitive (29.5%) included: difficulty concentrating, difficulty remembering, foggy, sensitivity to noise, feeling slowed down, visual problems, sensitivity to light, drowsiness; somatic (3.9%) included: vomiting, dizziness, nausea, numbness-tingling, headache, balance problems, sleep (3.2%) included: sleeping less, trouble falling asleep, fatigue; emotional (2.2%) included: feeling emotional, sadness, nervousness, irritability. For the individual symptom items, females reported significantly higher symptom scores (p < .001) for headache, .57 ± 1.1 vs .43 ± .96), irritability (.41 ± 1.0 vs .28 ± .83), nervousness (.43 ± 1.0 vs .33 ± .87), feeling emotional (.48 ± 1.1 vs .19 ± .69), sadness (.36 ± .93 vs .26 ± .77) and sleeping less (.72 ± 1.3 vs .61 ± 1.2). Conclusions: Sex differences were noted in both the baseline factor structure and severity reports of some individual symptom items. While the general factor categories were similar, there were differences in the loading of some symptoms including: sensitivity to noise and light, balance problems, numbness and irritability. Clinicians should expect higher baseline symptom scores in female athletes and take this into account during the post-injury assessment of symptoms and over the course of recovery. Future studies should continue to evaluate the psychometric properties of the symptom scale to develop an evidence-based symptom evaluation for concussion assessment.