Background Persistent changes in sexuality often follow traumatic brain injury (TBI). However, health professionals remain reticent about discussing sexuality and have reported barriers including uncertainties around whose role it is and limited educational and institutional support. This study employed a co-design and implementation process, aiming to promote team-wide behavioural change, whereby health professionals at a TBI rehabilitation unit would attempt to address sexuality with patients routinely. Methods Focus group sessions with multidisciplinary health professionals were conducted to identify barriers and enablers to behavioural change, identify areas for development, and co-design intervention options. Implementation deliverables were then finalised and provided to the team. The Theoretical Domains Framework was used to map factors influencing behaviours and the Behaviour Change Wheel was used to map interventions. Thematic analysis was used to further analyse barrier themes. Results Thirty-five barriers and eight enablers falling within 12 theoretical domains to behavioural change were identified. Thematic analysis revealed highly correlated barriers in initiating and sustaining change. Nine co-designed intervention options aligned with five intervention functions of the Behaviour Change Wheel, resulting in six final implementation deliverables. Conclusions Barriers were highly interrelated, influencing the approach to implementation deliverables. Simultaneously addressing multiple barriers could potentially alleviate discomfort associated with discussing sexuality. Concerns around initiating change were related to confidence in achieving sustainable changes. Achieving change requires organisational and team-level environmental restructuring and enablement. The next step involves evaluating the effectiveness of the co-design and implementation process in driving behavioural change and potential impacts on patient satisfaction and sexuality outcomes.