Purpose: Post-traumatic stress disorder (PTSD) is a known potential sequel to physical trauma. However, there is disagreement regarding the predictors of this condition. Furthermore, PTSD in trauma patients has seldom been studied in New Zealand. This study aimed to measure the prevalence and predictors of PTSD amongst hospitalised trauma patients in New Zealand. Methodology: Participants were recruited from the NZ Major Trauma Registry (NZ-MTR; Injury Severity Score [ISS] ≥ 12). Eligible participants were mailed a questionnaire containing a series of self-reported 5-point rating scales that assesses DSM-V symptoms of PTSD. Baseline characteristics and demographic data were obtained from the NZ-MTR. Correlation coefficients and t-tests were used for determining predictors of PTSD scores. Results: Among 210 patients with major trauma (24.9% response rate), 38 (18.1%) were classed as having PTSD. Symptoms of PTSD were positively associated with the presence of anxiety (r = 0.80, <.001) and depression (r = 0.75, p < 0.001); higher ISS (r = 0.17, p = 0.02), and years since injury (r = 0.16, p = 0.02). PTSD was negatively associated with older age (r = -0.24, p < 0.001), and perceived social support (r = -0.46, < 0.001). There was an insignificant trend towards females scoring higher than males (18.15 vs 14.35, p = 0.10). Conclusion: High rates of PTSD exist in patients following major trauma in NZ. Patients with pre-existing anxiety and depression, a higher ISS, younger age, more time since injury, and who lack social support, are at a higher risk of developing PTSD.