OBJECTIVE To identify factors associated with post-concussion syndrome (PCS) among a national sample of high school student-athletes from the 2011/12-2013/14 academic years. METHODS Ambispective cohort study from sports injury surveillance data. METHODS Sport-related concussion data originated from the National Athletic Treatment, Injury and Outcomes Network (NATION) surveillance program, consisting of 27 sports from a convenience sample of 196 high schools across 26 states. All SRCs were reported by certified athletic trainers. The PCS and non-PCS groups consisted of concussed individuals with symptoms resolution time of >4 weeks and ≤2 weeks, respectively. Logistic regression estimated the association of athlete and concussion characteristics on the odds of PCS, and calculated adjusted odds ratios (OR) and 95% confidence intervals (CI). RESULTS Overall, 1334 concussed high school athletes met inclusion criteria: 215 in the PCS group and 1119 in the non-PCS group. In the multivariable analysis, concussion symptoms associated with increased odds of PCS included: retrograde amnesia (OR=3.01, 95%CI: 1.31-6.91), difficulty concentrating (OR=2.72, 95%CI: 1.56-4.77), disorientation (OR=1.86; 95%CI: 1.04-3.33), insomnia (OR=2.79; 95%CI: 1.62-4.80), loss of balance (OR=1.76; 95%CI: 1.00-3.10), sensitivity to noise (OR=1.80; 95%CI: 1.02-3.17), and visual disturbance (OR=2.21; 95%CI: 1.23-3.97). Sex and recurrent concussion were not associated with PCS. CONCLUSIONS As in previous research, somatic and cognitive symptoms were associated with PCS. The identification of factors associated with PCS may assist clinicians in identifying concussed athletes at greater risk of having longer symptom resolution time.