Abstract: Because of very limited information of the clay minerals of Southern Jazan region (Saudi Arabia), the mineralogy of the clay fraction has been studied. A total of nineteen soil samples from five sites representing the main landforms in the region were studied. X-ray diffraction, differential thermal and thermo gravimetric analyses were carried out on the samples. Smectite, kaolinite and illite were found to be the predominant soil minerals. Other minerals present in small quantities included: Chlorite, quartz, feldspars. DTA confirmed the low hydroxylation temperatures of kaolinite (513-540°C), which indicates disordered crystallization of kaolinite. Moreover, TGA illustrated 4-6.6% (average 5.4%) weight loss related to dehydroxylation of kaolinite. Therefore, the amount of kaolinite minerals was calculated to be 29-47% with average 39%. The clay minerals in the samples were similarity among all the sites and this could be explained by the fact that arid conditions found in the area does not support intense pedogenic processes.