Oases throughout the world have become important ecosystems to replenish food and water supplies. The Saharan Oases exist above the largest underground water supplies in the World. In North Africa, oases witness significantly growing populations in the oasis towns and receive thousands of tourists yearly. In oasis settlements, the majority of the population spends most of the time outdoors, in extremely hot conditions; however, few studies have investigated urban outdoor thermal comfort conditions. Therefore, this study aimed to assess thermal comfort in the Tolga Oasis Complex and test the validity of the ‘oasis effect’ concept. The methodology is based on comparative field measurement and calculation approaches in the heart of Tolga Palm Grove and in different urban settlements. Results indicate highest heat stress levels (Physiologically Equivalent Temperature (PET) index) in the oases Palm Grove in July, PET = 41.7 °C, and urban settlements, PET = 40.9 °C. Despite the significant difference between the old and new settlement fabrics, our measurements and calculation did not identify any noticeable variation of thermal comfort. Thus, the oasis effect on the outdoor thermal comfort was insignificant (during July and August 2018). Finally, the study discusses ways to improve outdoor spaces design and relieve heat stress in the settlements of Tolga.