This paper reviews recent research trends in pedestrian detection in low-light environments. Although there are many studies on pedestrian detection using visible-light images during the day, they are difficult in low-light or nighttime environments. This paper examines recent research on utilizing far-infrared (FIR) temperature sensor data as an alternative for pedestrian detection in low-light environments. We systematically classify and analyze various algorithms such as region-based, region-less, and graph-based learning methodologies, and emphasize the methodology, implementation issues, and challenges of each algorithm. In addition, we present key benchmark datasets that can be used for research and development of advanced pedestrian detection algorithms, especially in low-light situations.