<p>Understanding how rehabilitant animals progress in survival-related skills could support more sustainable releases, but this requires a valid and feasible method tailored to rehabilitation settings. Consisting of two parts, this project adapted a rating tool to measure sun bear behaviours which was then focussed on 20 rehabilitant sun bears from the Bornean Sun Bear Conservation Centre, Sabah, Malaysia. In part 1, we tested the reliability and validity of each rating item and systematically identified a subset of valid items based on pre-set criteria. In part 2, scores from reliable and valid questionnaire items were used to determine whether opportunities to practice, sex and personality traits predicted the progression of important climbing and nesting behaviours. Through cumulative link mixed modelling, we identified a number of significant predictors. Specifically, sun bear subadults whose exposure to a forest environment is still novel, exhibited important climbing and nesting skills more often than adult sun bears with prolonged forest enclosure exposure. This work was limited by the absence of cubs during a critical development period; however, it provides an initial framework that underscores the importance of including behavioural skill assessment to monitor sustainable sun bear rehabilitation.</p>