This study aims to analyze the relationship between Indoor Environmental Quality (IEQ) and workers' satisfaction and performance levels in LEED certified office buildings. to provide useful information and design recommendations for buildings designers as well as decision makers regarding which IEQ criteria elements improve or worsen workers' satisfaction and performance levels in sustainable environments. Despite a recent increase in popularity and implementation of sustainable building design practices, little research has been done on the effects of these guidelines on worker satisfaction and performance in LEED-certified buildings. Knowledge about the influence of the physical work environment on office worker satisfaction and performance is critical to businesses' economic success. Worker satisfaction and performance underpins employee recruitment, retention, health, and welfare in the workplace. Understanding how sustainable building design is related to workers' satisfaction and performance will also help enhance the current sustainable building design movement and continue the successful market transformation led by the USGBC. The IEQ criteria included in this study are user perception of quality of office layout, office furnishings, thermal comfort, indoor air, lighting, acoustics, cleanliness and maintenance, and overall workspace. Worker satisfaction and performance were measured by a user self-assessment questionnaire administered through an on-line survey. Respondents' demographic characteristics and office characteristics were also collected and analyzed.   Correlational statistics were used to determine the relationship between IEQ criteria and worker satisfaction and performance. Respondents' demographics and office characteristics were analyzed using descriptive statistics and used to describe the workspaces. Descriptive statistics were also used to summarize the participants' responses in each IEQ criterion. This study contributes to interior designers' knowledge and ability to incorporate effective IEQ criteria to support worker satisfaction and performance in sustainable workplaces. The findings will enable businesses to make appropriate sustainable design decisions that may affect their business strategies. They will also help identify the strengths and weaknesses of the current IEQ criteria in the LEED-certification system that influence work environment. This knowledge may increase the use of LEED system by designers and business owners, thereby supporting the sustainable building design movement and contributing to the successful market transformation.