The traditional construction industry has a significant and far-reaching impact on the environment, economy, and society. Green-certified buildings, with LEED (Leadership in Energy and Environmental Design), BREEAM (Building Research Establishment Environmental Assessment Method), DGNB (Deutsches Gütesiegel Nachhaltiges Bauen), or other certifications during the design stage, have great potential for increasing the effective use of resources and energy, reducing pollution, etc., and so their number has increased greatly in recent years. The post-occupancy evaluation (POE) of green buildings involves assessing whether they meet expected performance during the in-use phase and comprises four steps: (i) carrying out the research purpose/goal; (ii) determining the research objectives; (iii) conducting data collection, analysis, and visualization; and (iv) obtaining the results and drawing conclusions. However, there is a lack of reviews of POE research and analysis of reasons for actual performance gaps. In response and through a comprehensive literature review/analysis, this article summarizes the actual performance gaps of various greencertified projects, analyzes the reasons for failures, and proposes potential solutions. It is found that 74%, 12%, and 14% of the projects perform better, similar, and worse, respectively, than their non-green counterparts. Future POE green building projects can be optimized from the perspective of the building, user, and POE system. To optimize green building actual performance, it is important to ensure the sufficient education of installation and maintenance personnel and occupants’ green behavior, while interior design and decoration, the impact of user demographics, and POE performance indicators are key factors to be considered in green building design strategies and lifecycle evaluation systems.