Modular residential construction activities often require prolonged standing, bending, stooping, and material handling, while working in crowded spaces; these activities increase the potential risk of work-related musculoskeletal disorders (WRMSDs), which may worsen over time, resulting in permanent disability and, consequently, the loss of ability to work. The use of system dynamics (SD) modeling to assess ergonomic risks provides a decision support tool for job managers and job designers and delivers a powerful graphical illustration, showing the logical links between cause and effects and helps illustrate how ergonomic risks may lead to WRMSDs. This paper presents a SD model for ergonomic analysis of residential construction tasks. A case study is presented and used to evaluate variations in risk exposure to identify most contributing factors to potential ergonomic injury. Also a literature review is performed to identify the main ergonomic risk variables. The results are expected to assist project participants in controlling and assessing ergonomic risks leading to improved work efficiency, safety and reduced lost time injuries and related cost, insurance premium (WCB) and claims caused by WRMSDs.