This study examines whether capital structure determinations by Indonesian publicly listed firms (Tbks) are influenced by the behavioural biases of overconfidence and optimism, with the underlying rationality frameworks being framed by relevant financial information and impacted by decision-makers’ demographic attributes. Data were obtained from survey respondents and statistically analysed using partial least squares structural equation modelling to identify the indicators of causative dynamics within the hypothesised relationships. Sampled Tbks’ management (CEOs/CFOs) displayed the inherent behavioural traits of overconfidence and optimism in their capital structure determinations. However, such behavioural variables were not statistically proven to significantly influence capital structure decision-making and, hence, were not validated as capital structure determinants. The pecking order framework was revealed to have a significant framing effect on capital structure decision-making by sampled managers. Sampled managers’ demographic attributes and backgrounds were found to be capital structure determinants but did not have a mediating or moderating influence on the modelled relationship between behavioural variables and capital structure.