Study 1 examined the association between intensity of postconcussive symptoms (PCS), impact of daily stress, and level of perceived stress over the past month in a group of healthy young adults. There was a significant relationship between intensity of PCS and impact of daily stress, as well as level of perceived stress over the past month, independent of the frequency of stressful events experienced. Study 2 assessed the stability of the relationship between PCS and stress. Subjects rated intensity of PCS, impact of daily stress, and level of perceived stress on two separate occasions approximately 1 month apart. The Perceived Stress Scale demonstrated high test-retest reliability. Significant relationships were again found between intensity of PCS and level of perceived stress at both time points, independent of the frequency of stressful events. These results suggest that persistent symptoms in some individuals with postconcussive syndrome may be due, at least in part, to individual differences in the perceived stress of incurring a mild traumatic brain injury.