Post-traumatic growth (PTG) can emerge following traumatic brain injury (TBI), however measures of PTG rely on the cognitive capacity to reflect on psychological growth. Positive associations between scores on PTG measures and behavioural and functional indicators of growth would help establish the clinical utility of measuring PTG after TBI. We examined the degree of association of the Post-traumatic Growth Inventory - Short form (PTGI-SF) and Changes in Outlook Questionnaire - Short form (CiOQ-S), with (1) PTG-consistent behaviours; (2) valued living (behaving in ways consistent with one's values); and (3) post-injury functional outcomes. Participants had moderate to severe TBI and were 1-5 years post-injury (n = 70). Participants with higher scores on the CiOP-S (the positive subscale of the CiOQ-S) reported more frequent PTG-consistent behaviours post-injury, such as showing care towards family and friends, and appreciation of life. Higher CiOP-S scores were also positively associated with valued living and return to work/study. There were fewer associations between PTGI-SF scores and behavioural and functional outcomes. PTG after TBI, as measured by the CiOQ-S, was associated with behavioural and functional indicators of positive growth, highlighting the strength and utility of this scale and the importance of measuring and fostering PTG in rehabilitation.