Injury is a leading cause of disability and is costly. This prospective cohort study extension aims to improve disability, health, and wellbeing outcomes for injured New Zealanders, including for Māori. We will identify predictors and modifiable risk factors of long-term outcomes (positive and negative), and develop an Injury Early Care Tool (INJECT) to inform the implementation of effective interventions to improve outcomes. In the Prospective Outcomes of Injury Study (POIS), 2856 people participated following an injury (occurring between 2007 and 2009) registered with New Zealand’s no-fault accident compensation scheme (ACC). POIS-10 will invite 2121 people (including 358 Māori) who completed a 24-month POIS interview and agreed to follow-up, anticipating 75% participation (n = 1591). Interviews will collect sociodemographic characteristics, life events, comorbidities, and new injuries since participants’ 24-month interview, as well as key disability, health, and wellbeing outcomes 12 years post-injury. Injury-related data will be collected from ACC and hospitalisation records 12 years post-injury. Regression models for the main outcomes will examine the direct effects of predictor variables after adjustment for a wide range of confounders. POIS-10 is enhanced by our partnership with ACC, and expert advisors and will benefit injured people, including Māori, through increased understanding of mechanisms and interventions to improve long-term post-injury outcomes.