The ecological nature of the organization is one of the important topics discussed in the field of the theory of durable and sustainable development and CSR practices. What is more, being a "green organization" has become not only fashionable but also beneficial. Ecological issues are discussed in many documents formulated by private and public entities. Many organizations try to call themselves "green" or "sustainable", but there is no consistent definition of a green organization. The aim of this article is to define a green organization and to identify challenges for their development. The article adopts qualitative methods that distinguish three main aspects of the possible definition of green organizations.