The building industry is blamed for consuming enormous natural resources and creating massive solid waste worldwide. In response to this, the concept of circular economy (CE) has gained much attention in the sector in recent years. Many pilot building projects that implemented CE concepts started to appear around the world, including Taiwan. However, compared with the pilot projects in the Netherlands, which are regarded as the pioneer ones by international society, many CE-related practices are not implemented in pilot cases in Taiwan. To assist future project stakeholders to recognize what the key CE-related practices are and how they could be implemented in their building projects in Taiwan, this study has conducted a series of case studies of Dutch and Taiwanese pilot projects and semi-structured interviews with key project stakeholders of Taiwanese pilot projects. Thirty key CE-related practices are identified via case studies, along with their related 5R principles (Rethink, Reduce, Reuse, Repair, Recycle) and project phases. Suggestion on CE-related practices, their 5R principles, project items, and phases to implement in building projects in Taiwan is also proposed while discussion on differences between two countries’ pilot projects is presented.