The discipline of knowledge management (KM) considers knowledge as potentially the most valuable organisational asset that must be shared among staff and stakeholders and even communities in order to yield considerable returns and benefits. However, in a real-world context, managers in industries such as high technology, manufacturing and finance jealously guard their valuable knowledge and prevent other entities from gaining access to this resource. Open cases of knowledge sharing among stakeholders such as staff, customers, business partners, competitors and the public are rare. Therefore, the philosophical premise of KM -- "knowledge must be openly shared" -- is often unrealised. Knowledge of environmental sustainability is a valuable resource for ecotourism operators because they operate in natural environments such as the Great Barrier Reef in Australia and Sipadan Marine Park in Malaysia, and depend on the quality of these environments for their ongoing success. This research provides evidence that knowledge dissemination in the form of environmental sustainability knowledge can be openly shared among staff, customers, competitors and the public, thereby linking KM and environmental education. This article provides an interpretivist analysis of knowledge sharing by innovative ecotourism operators in Australia and South East Asia (Malaysia and Thailand). Data were collected through in-depth interviews with 14 executives, field observations and analysis of company documents. Results from this research found that ecotourism managers are passionate believers of environmental sustainability and benevolently share their valuable organisational knowledge and beliefs with all stakeholders.