Semi-outdoor learning space is an important part of a university campus, as it accommodates learning and social activities while enabling users to connect with outdoor environments. This research explores the relationships between thermal environments, thermal perceptions and spatial settings in five selected semi-outdoor spaces on the campus of the National University of Singapore. A distance meter was used to measure spatial settings such as the floor height and void-to-solid ratio in the selected spaces. A heat stress meter was used to measure air temperature and relative humidity, and another meter to measure wind speed. A questionnaire survey was carried out to collect the users’ thermal perceptions. A total of 339 students were involved in the survey. The results of the study indicated that increasing the height of the space and the height of surrounding buildings can increase users’ satisfaction with semi-outdoor space. In terms of architectural design, the temperature and wind speed can be effectively regulated by building orientation and the void-to-solid ratio, respectively. This study provides evidence and guidelines for campus planning and design.