Indoor environmental quality (IEQ) is important to the health, comfort, and well-being of building occupants. Unsatisfactory IEQ is associated with a number of phenomena, most notably, sick building syndrome (SBS), building-related illnesses (BRIs), and multiple chemical sensitivity (MCS), which have major negative effects on productivity. However, green building investors (owners) are not only concerned about reducing the negative impact of their buildings on the environment, but also about the potentially negative impact green buildings can have on their employees' productivity. This research sets out to address, through a questionnaire survey in South Africa, what constitutes the determinants of green building occupants' satisfaction with the IEQ elements of a green building and the health implications of a building's IEQ on the building occupants. Data analysis (involving a one-sample t-test) reveals some interesting findings in regard to what constitutes the determinants of green building occupants' satisfaction with the IEQ elements and the health implications of the IEQ elements of a five-star green rated building in South Africa. Findings from the survey revealed that the occupants of the building were not satisfied with the green building's IEQ, most especially the ineffectiveness of blocking natural and artificial lighting. Also, it was revealed that the IEQ with particular reference to the noise level and ventilation of the space has some serious health implications for the building occupants. The occupants' evaluation revealed that the major health issues from which they suffer include fatigue, headache, common cold, coughing, and influenza, and these affect their productivity and performance. Since building occupants are a rich source of information about IEQ assessment and its effect on productivity, the study can be used to assess the performance of green buildings, identify areas needing improvement, and provide useful feedback to designers and operators about specific aspects of green building design features and operating strategies that need improvement. This study adds to the body of knowledge on green buildings' IEQ performance.