Background <p>Traumatic brain injury (TBI) causes major societal burden and may negatively influence an individual’s health-related quality of life (HRQoL). Personality factors have been linked to persistent post-concussion symptoms (PPCS), and PPCS have been found to affect HRQoL. However, there is a knowledge gap concerning the association between personality traits and HRQoL after mild-to-moderate TBI. Thus, this study aims to investigate the association between personality traits and HRQoL in patients with mild-to-moderate TBI at 15 months post-injury, while controlling for socio-demographic characteristics, injury-related factors and symptom burden.</p> Methods <p>Data from 86 participants with mild- to-moderate TBI from a previous randomised controlled trial were analysed. Sociodemographic, injury-related and psychological factors were recorded 2–3 months post-injury. Personality traits were measured at 15 months post-injury with The NEO Five-factor Inventory-3. The Quality of Life after Brain Injury– Overall Scale (QOLIBRI-OS) and the EuroQol-visual analogue scale (EQ-VAS) were used to measure HRQoL at 15 months post-injury. Two separate multiple linear regression models were performed for the outcome variables; QOLIBRI-OS (model 1) and EQ-VAS (model 2).</p> Results <p>The factors associated with lower HRQoL were more severe PPCS, higher levels of the personality traits neuroticism and conscientiousness (model 1), female sex and being single/living alone (model 2). Higher levels of the personality trait extraversion were associated with higher HRQoL in both models.</p> Conclusion <p>The results highlight how non-injury factors may be associated with recovery and HRQoL after TBI. Considering personality factors may be helpful when identifying individual risk and protective factors for outcomes after mild-to-moderate TBI.</p>