Complex systems like the built environment cannot be understood by studying parts in isolation. The very essence of the built environment complex system lies in the interactions between parts and the behaviour that emerges from these interactions. Built environment systems must be analysed as a whole and achieving this goal will require a shift in current built environment research. The new focus should be on coordinated built environment research through developing interoperable complex systems to address the needs for integrated systems, in order to optimize and deliver future sustainable built environment. Complexity theory is poised to propel research into the built environment beyond the traditional approaches. To harness this fundamental paradigm shift in understanding real-world complex problems, Embracing Complexity in the Built Environment, a special issue of the journal Architectural Engineering and Design Management, provides insight into the theory and application of complexity techniques for modelling some of the built environment problems. It includes discussion of the importance of complexity for the built environment research agenda to introduce new users to the potential and pitfalls of this research paradigm. Embracing Complexity in the Built Environment will significantly augment the intellectual basis of the discipline and will expand considerably the boundaries of the built environment research agenda. Given the importance and novelty of complexity theory, this publication will be of great value to academics, professionals, and both undergraduate and postgraduate students.