Occupants play a key role in determining final building energy consumption. Empirical evidence must support occupants' modelling. Experiments on human responses to Indoor Environmental Quality (IEQ) are usually performed in test rooms or as in-field monitoring. Between these two approaches, living laboratories, often abbreviated as living labs, represent a valid alternative due to their resemblance to real-world settings. This allows observing actual behaviours while keeping the capability to reliably monitor and control the indoor environment. This work systematically reviewed the available information from 34 living labs for human comfort studies worldwide to define the scope, characteristics, and significance of living labs, for the first time. Most of the reviewed living labs are office environments, and only a few do not involve a university research institution in their operation and management. Most of them are in Europe and the United States, whereas there is a lack of such facilities in other locations and climate zones (e.g., tropics). A larger number of comfort studies in living labs is required to clarify the differences in the knowledge acquired in these experiments compared to in-field and laboratory ones. The review shows that living labs add opportunities for testing and optimizing innovations in human-centric solutions for comfortable green buildings. Through the living labs approach it is possible to holistically capture the influence of IEQ on occupant perception and the related response, to gather data on larger and more diverse groups of people, and to conduct multi-domain comfort studies involving multidisciplinary approaches given their real-life settings.