Green building (GB) projects in the Middle East encounter several causes of waste during design and construction phases, impacting their economic, environmental, and social goals. This study aims to identify these causes of waste and assess their impact on project objectives. Forty-five causes are identified and classified into five categories: G01) Green Materials, (G02) Green Building Design, (G03) Sustainable Site, (G04) Green Building Technologies, and (G05) Green Building Stakeholders. Field surveys, including semi-structured interviews, brainstorming sessions, and a questionnaire, are conducted to evaluate each cause's impact on GB goals. The findings reveal that the most significant cause of waste, with the highest influence on GB objectives, is “Poor assessment of site conditions before design, such as topography, hydrology, climate, vegetation, and soil.” Additionally, the cause of waste, which refers to the Lack of experience of green building designers, contractors, subcontractors, and suppliers in executing green buildings, is also a critical factor, as it highly affects the project objectives. This study helps project managers identify the key causes of waste in green building projects during the design and construction phases and develop strategies to minimize their effects. In addition, designers and decision-makers can use these insights to ensure they meet the requirements of various green building rating systems such as LEED (Leadership in Energy and Environmental Design).