Public safety personnel (PSP; e.g., border services personnel, correctional workers, firefighters, paramedics, police, public safety communicators) are frequently exposed to potentially psychologically traumatic events. Such events contribute to substantial and growing challenges from posttraumatic stress injuries (PTSIs), including but not limited to posttraumatic stress disorder. The PSP PTSI Study has been designed to evaluate an evidence-informed, proactive system of mental health assessment and training among Royal Canadian Mounted Police (www.rcmpstudy.ca) for delivery among diverse PSP (i.e., firefighters, municipal police, paramedics, public safety communicators). The training is based on the Unified Protocol for the Transdiagnostic Treatment of Emotional Disorders, adapted for PSP, and named Emotional Resilience Skills Training (ERST). Specifically, the PSP PTSI Study will: 1) adapt, implement, and assess the impact of a system for ongoing (i.e., annual, monthly, daily) evidence-based assessments; 2) evaluate associations between demographic variables and PTSI; 3) longitudinally assess individual differences associated with PTSI; and, 4) assess the impact of providing diverse PSP with a tailored version of the ERST originally developed for the Royal Canadian Mounted Police in mitigating PTSIs based on the Unified Protocol for the Transdiagnostic Treatment of Emotional Disorders. Participants are assessed at pre-training; week 1 (i.e., Time 1) and post-training; week 13 (i.e., Time 2), and then at a 1-year follow-up after training, during week 65 (Time 3). The assessments include clinical interviews, self-report surveys including brief daily and monthly assessments, and daily biometric data. The PSP PTSI Study hypotheses were pre-registered with aspredicted.org for the PSP PTSI Study and associated hypotheses occurred on March 7, 2022 with the name, "An Augmented Training Program for Preventing Post-Traumatic Stress Injuries Among Diverse Public Safety Personnel" (#90136). Hypotheses specific to individual difference variables are publicly available; however, the overarching PSP PTSI Study hypotheses are: 1) participant mental health disorder prevalence at Time 1, based on Clinical Interviews or screening tools based on self-reported symptoms, will be higher than would be expected for the general population; 2) from Time 1 to Time 2, participants will evidence reductions in risk, increases in resiliency, and improvements in mental health, as a function of the ERST; 3) participants will evidence statistically significant predictive relationships between completing assessments and changes to individual differences over time (i.e., inversely with risk, positively with resilience, positively with mental health); 4) participants will evidence statistically significant sequential predictive relationships for environmental factors or individual differences reported during the Daily Assessments, Monthly Assessments, and Full Assessments; 5) all participants will evidence sustained reductions in risk, increases in resilience, and increases in mental health at Time 3 relative to Time 2; 6) participants will evidence a statistically significant relationship between changes in individual differences over time and engagement with ERST content; 7) participants will evidence a statistically significant relationship between changes in environmental factors or individual differences over time, frequency of exercise, and other self-reported indicators of physical health; 8) relative to men, women will report more difficulties with mental disorder symptoms and occupational stressors; 9) diastole will be reduced in PSP who report symptoms consistent with one or more PTSI; 10) the biometric data will be statistically significantly and substantively correlated with measures of PTSI; 11) there will be a statistically significant and substantive relationship between PTSI symptom severity and reduced diastolic function; and 12) changes in biological variables (i.e., autonomic nervous system reactivity, heart rate variability, cardiac mechanical changes) will be associated with environmental factors or individual differences. The subsequent PSP PTSI Study results are expected to benefit the mental health of all participants and, ultimately, all PSP.