Mining industry has a wide range of activities and work stages which involve mining workers, starting from general investigations, explorations, to reclamation. It is considered as one of the industries with a high-level risk. Mining workers are synonymous with shift and roster work patterns, and physical work that requires strength, flexibility and endurance of sustained muscles that contribute to fatigue. Generally, fatigue is defined as a state of weariness due to prolonged wakefulness, long work periods, and is characterized by decreased alertness, impaired decision making, and reduced capacity for neurobehavioral performance (Akerstedt, 1995; Dinges, 1995). The purpose of this study is to determine the average alertness score of exploration drilling service workers in coal mines which is influenced by the level of fatigue of workers calculated based on the quality and quantity of sleep using the SAFTE Fatigue Model. This research is a quantitative descriptive cross-sectional design, from June to August 2019. The results state that the majority of respondents have an alertness score in the reduced category (66.67%). The cross variable distribution shows that the lowest proportion of alertness is in the age group of 31-40 years (50.00%), moderate sleep quality (70.00%) and quantity of sleep poor (33.33%). There are differences in alertness scores between morning shift and night shift respondents, and that is the night shift has lower average alertness scores than morning shift respondents. The recommendations of this study are to improve sleep hygiene by providing health education, ensuring optimal room temperature and adequate exposure to natural lighting, and minimizing the exposure to noise and gadgets..