Higher learning institutions in Africa have been investing in various eLearning systems (also referred to as learning management systems) aiming at improving the quality of teaching and learning. However, non-use or low usage of these systems amongst users is a significant setback for their success. Studies indicate that first-order barriers such as unreliable electricity power, shortage of computers, and Internet connectivity inhibit users from using these systems. This study examined system self-efficacy amongst instructors using mixed sequential explanatory design with data collected from 357 instructors at the University of Dodoma through questionnaires followed by focus group discussions. The adapted independent factors: performance accomplishments and vicarious experience from Bandura (1977), and organizational support from Higgins and Compeau (1995) were subjected to linear regression analysis to determine the causal relationship with system self-efficacy. The study found that vicarious experience and organizational support had a significant effect on system self-efficacy amongst instructors. These findings show that examining system self-efficacy amongst instructors is critical to help those who are implementing eLearning systems in finding strategies that will increase system usage.