CONTEXT: Neurocognitive testing is a critical tool in management of sports-related concussions. Adversity during childhood and adolescence effects cognitive tasks, behavioral outcomes, and academic performance. Adversity may be important in baseline concussion test validity as well; however, the effect of these experiences is not well understood. OBJECTIVE: This study examined the relationship between individual-level experiences of adversity and baseline test validity of the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) Program. We hypothesized that experiences of poverty, maltreatment, or extreme neighborhood deprivation would be associated with lower odds of baseline test validity. DESIGN: Case-Control Study. SETTING: XXX. PARTICIPANTS: This study included 6,495 student-athletes born between 1995 and 2005 who completed a baseline ImPACT test between 10 and 18 years old and could be identified in the Child-Household Integrated Longitudinal Data (CHILD) System, a comprehensive data system with demographic and social service usage outcomes for children in XXX. MAIN OUTCOME MEASURES: Baseline concussion test validity was determined using the ImPACT program’s built-in validity measure. Experiences of adversity occurring in the sensitive developmental periods of early childhood and adolescence were key independent variables. RESULTS: Our findings suggest that social mobility may play an important role in baseline validity. Youth with upward social mobility (poverty or neighborhood deprivation in early childhood only) were not significantly different than youth without such experiences (OR=0.91, p=0.74). Youth with persistent adversity across childhood or downward social mobility (poverty or high neighborhood deprivation in adolescence only) had 50-72% lower odds of achieving a valid baseline test (persistent poverty: OR=0.59, p=0.05; adolescent poverty only: OR=0.50, p=0.004; adolescent neighborhood deprivation only: OR=0.28, p<1.0e-4). Maltreatment had no significant effect on test validity. CONCLUSION: These findings suggest certain patterns of adversity may predispose youth to invalid baseline testing scores, potentially increasing their risk of inaccurate injury management and poor outcomes.