Youth and young adults who previously experienced foster care are prone to negative life events, such as physical injuries, and adverse childhood experiences (ACE), such as abuse, neglect, and household dysfunction. The purpose of the present study was to identify the prevalence of traumatic brain injury (TBI), ACE, and poor sustained attention and the associations of these events in this group of vulnerable persons. Participants completed standardized questionnaires on the prevalence of self-reported TBI (TBI) and ACE and performed the Sustained Attention to Response Task (SART) test to measure sustained attention. Chi-squared and Kruskal-Wallis rank-sum tests were used to assess demographic differences and associations between TBI and ACE. Sustained attention was assessed using analysis of variance and linear modeling. Seventy-one participants—46 youth and young adults who previously experienced foster care (vulnerable group) and 25 age-matched healthy controls— completed the standardized questionnaires. Analyses indicated that vulnerable participants reported markedly higher rates of TBI and ACE than healthy controls. Vulnerable persons with TBI reported significantly higher Total ACE scores (p = 0.02), were more likely to have a history of family dysfunction ( p = 0.02), and were more likely to have lived with a mentally ill guardian ( p = 0.01) than vulnerable persons with no TBI. TBI was significantly associated with Total Errors ( p = 0.001 and p = 0.02) and Omission Errors ( p < 0.001 and p = 0.01) in all participants and in vulnerable participants, respectively, after adjusting for education level.