<p>Cognitive fatigue, which is caused by the mental and physical workload associated with executing occupational tasks, has been recognized as a leading cause of human errors and associated accidents in various industries worldwide. Mining jobs that require a high level of human involvement are not an exception to this. The objective of the present study is to decipher the cognitive fatigue among Side Discharge Loader (SDL) operators and its relationship with demographic, occupational, and workload factors. There is a limited number of studies that have highlighted the evaluation of cognitive fatigue experienced by workers in such a demanding operation. This study focused on addressing specific aspects of the job performed by 150 male SDL operators. Firstly, the study evaluated the cognitive fatigue among SDL operators through a Psychomotor Vigilance Task (PVT), which provided the number of lapses as the objective measure of fatigue. Secondly, workload factors were evaluated using the NASA-TLX subjective assessment. The study results suggested that the task-related exertions resulted in cognitive fatigue, which was manifested as an increase in the median number of lapses from 2.5 at the rest state to 11 at the post-work state (Z = 10.38, <i>p</i> &lt; 0.001). Among the demographic and occupational factors considered, a gradual increase in the mean number of lapses was observed across the four categorical age groups (1.14 vs. 2.02 vs. 2.89 vs. 3.87) and two categories of years of experience (2.28 vs. 4.18). Out of six workload factors, mental demand, physical demand, performance, and frustration were found to be significantly associated with cognitive fatigue. The presence of cognitive fatigue was primarily due to task-related demands and the difficulty of maneuvering the machine in underground mines. Intervention techniques such as periodic fatigue assessment, well-being, and safety plan focusing on stress and fatigue management of the SDL operators were found necessary.</p>