We estimated the environmental impact and financial cost of two exemplar in-person academic events organised by the European academic society, the European Academy of Nursing Science, identified the main sources of these emissions, and then mapped them against the COM-B behaviour change framework of capability, opportunity, motivation to identify strategies that could be applied by organisers and participants to reduce this impact. These events contributed 41 tonnes and 99 tonnes of CO2e emissions per event, a per-participant mean of either 0.324 (SD 0.173) or 0.724, (SD 0.263) tonnes, representing 2 to 5.5 times the daily per-person European average. Distance from home was the largest contributor to emissions. Costs were similar for both events. Our multi-component behavioural change programme includes environmental change, enablement, education, incentivisation and persuasion, by which organisers provide participants with the opportunity for less-polluting behaviour, and enhance participants capabilities and motivation to act on the opportunities provided.