Trauma-informed practices in schools are designed to address the impacts of trauma on students and increase supports for school personnel who are delivering this care The impact of a trauma-informed school-based intervention. Journal of Adolescence, 43, 142–147, Mendelsonet al., 2015. Research has established that professionals trained to implement the approach may have secondary traumatic stress (STS) reactions that could interfere with successful implementation (Stevens al., 2020). In this study it was hypothesized that increased use of trauma-informed care strategies would be associated with decreases in total STS scores, as well as all STS subscale scores at the end of a system’s transformation initiative, controlling for sex, age, education, years worked in schools, and exposure to student trauma awareness at baseline. The Trauma Sensitive Schools Checklist (TSSC) and the Secondary Traumatic Stress Scale (STSS) were used to measure study outcomes in a sample of 205 school personnel at baseline and follow up. Statistically significant improvement in STSS scores and TSSC score were noted from Time 1 to Time 2. As hypothesized, improvements in TSSC scores were associated with decreased levels of STS over time, controlling for the covariates. However, the symptom domains of intrusion and arousal impacted this relationship in a differential manner than avoidance and alterations in cognitions and mood. This study provides evidence that increased use of trauma-informed care practices can positively impact the STS levels of school personnel, though special attention should be paid to those with high levels of intrusion or arousal.