Purpose - The purposes of this paper are to: investigate schedule performance of new and retrofitting green building projects; identify the critical factors that influence the schedule performance of new and retrofitting green building projects; and provide solutions to improve schedule performance of new and retrofitting green building projects. Design/methodology/approach - A questionnaire survey were conducted and responses were received from 34 firms experienced in green building projects in Singapore. After the data from the survey had been analyzed, face-to-face interviews were conducted with two senior project managers to solicit comments on the survey results. Findings - This study identified the degree of project delay in 98 new green building projects and 51 retrofitting green building projects in Singapore. The result indicated that 22 percent of the Singaporean green building projects were plagued with delay and retrofitting projects had a significantly higher likelihood of delay and significantly longer extension than new projects. In addition, "consultant cooperation to solve problems" was the most influential to schedule performance of both new and retrofitting green building projects, and the two project groups agreed on the overall ranking of the factors affecting schedule performance. Research limitations/implications - There may be geographical limitation on the conclusions drawn from the findings. Also, the sample size was still small, despite a relatively high response rate. In addition, the majority of the respondents were contractors as other project players were reluctant to respond to the survey. Practical implications - This study provides a clear understanding of the schedule performance of green building projects as well as the critical factors that should be highlighted when constructing green building projects. Also, strategies to overcome the negative impact of these factors allow practitioners to better deal with the potential causes of delay and to attain the schedule performance. Originality/value - Although construction delays have been widely investigated in previous studies relating to construction management, few have attempted to analyze the schedule performance of new and retrofitting green buildings. Thus, this study adds significantly to the existing research on both green building and construction delay.