This study investigates what an ecological sustainable (ES) special library can be, with the purpose to find out how it can be implemented. I have chosen one specific special library to see how they work with ES and I also make an attempt to find the difficulties of the ES work. In this work, I use practice theory to analyze how the concept of ES can be applied on a practical level. There is a lot of research on how ES is applied to library buildings when it comes to energy savings and the usage of recycling, but limited research on how it can be applied to the function or activity of the library. The data collected from five semi-structured interviews are presented, and my conclusions are that a special library has very good grounds for working with ES. Libraries can be role models in their ES practice since circulation is one of the fundamental functions of libraries. The focus of an ES special library should be in the practice of work at the library, rather than only energy savings and recycling. An ES special library should try to get hold of material that treats ES in some way from the special library’s perspective. The special library should incorporate the ES in events and in cataloguing of the ES materials, for example. Informing users and the society about its work and be a role model for others to follow are also important library practices.