One of the important ways of reducing the environmental problems caused by construction activities is disseminating green buildings. For this, experiences related to the green building process are important. The most important actors of the green building process are green building consultants. In this context, the research's main purpose is to explore the essence of green building consultants' perceptions of certification systems and their green building experience. Green building materials are also of great importance in creating green buildings. For this reason, the sub-purpose of this study was determined as the discovery of the essence of green building consultants' perceptions and experiences about the building material category in certification systems. The participants of this research, which is designed as a phenomenology research, are ten green building consultants. Within the scope of the research, the data were collected through in-depth interviews, reduced to key statements, and themes were reached. According to the results of the research; the essence of green building consultants' perceptions of certification systems and their experience in creating green buildings; learning to build environmentally friendly buildings and the change in the industry, interdisciplinary - joint work and integrated project management, increase in respect for the profession, increase in the quality of the contractor company, user comfort, marketing, and cost. The essence of the perceptions and experiences of green building consultants about the building material category is; environment and human health, life cycle assessment, raw materials and production, local materials, certified materials, reuse and recycling, waste management, cost, education, and sectoral transformation.