•A basic and comprehensive picture of research on occupant behavior and building energy performance is presented by systematic review of the literature.•Four critical research topics are identified.•Energy-saving potential of occupant behavior is discussed and estimated to be in the range of 10%−25% for residential buildings and 5%−30% for commercial buildings.•Four existing research gaps are identified and discussed. Technology alone will not achieve building energy conservation goals, and humans and their energy-related behavior in buildings must be included in energy performance efforts. Despite many studies revolving around human behavior and building energy performance, the understanding of occupant behavior and its role in building energy performance remains vague, confusing and inconsistent. We attempt to rethink occupant behavior and its role in building energy performance by means of review. Relevant articles have been collected from Web of Science and the basic picture of research has been presented. In-depth review focuses on four critical research topics: a) the current understanding of occupant behavior, with particular focus on window opening behavior, lighting control behavior, and space heating/cooling behavior; b) methods and techniques for collecting data on behavior and building energy performance; c) quantitative modeling of occupant behavior and building energy performance; and d) evaluation of energy saving potentials of occupant behavior based on existing literature. We estimate the energy-saving potential of occupant behavior to be in the range of 10%–25% for residential buildings and 5%–30% for commercial buildings, based on findings of existing research. From our analyses, we identify four existing research gaps, namely the needs for understanding occupant behavior in a systematic framework; for stronger empirical evidence beyond individual buildings and at a larger city scale; for linking occupant behavior to socio-economic and policy variables; and for evaluating the role of occupant behavior in the effectiveness of building energy efficiency policy.