Tremendous advances in computer technology and the evolution of the Internet have led to new approaches in learning and training which are summarized under the term e-Learning. This research studied the effects of e-learning system on teacher orientation programs conducted by Kenya Institute of Education (KIE), which is a National Curriculum Development and Research Centre, offers online teacher orientation courses using Elimika learning management system. The objectives of this study were to establish the extent of use of e-learning system by teachers in curriculum orientation programs, assess teachers' perceptions, identify challenges and establish possible mechanisms that can be put in place to encourage teachers to use e-learning system in curriculum orientation programs. Theoretical framework for the study was Technology Acceptance Model which postulates that a person's behavioural intention to use e-learning is determined by perceived usefulness and ease of use. The population consisted of 800 primary school teachers enrolled in Elimika e-learning system and 124 curriculum developers working at KIE. Stratified random sampling was used to select a sample of 214 teachers and 110 curriculum developers. The curriculum developers who responded to the questionnaire were 198 and teachers were 80 representing a response rate of 92.52 percent and 72.73 percent respectively. Data was collected using questionnaires and analyzed using Statistical Package for Social Sciences version 19. The study found out that e-learning system features such as ease of use, interactivity and flexibility had significant total effects upon usage by teachers in curriculum orientation. Also teachers' perceptions on the appropriate content, saving on time and effort, learning enhancement and enjoyment had a significant effect on intention to use Elimika system. The study also identified various challenges encountered by teachers and some mechanisms that can be put in place to encourage teachers to use e-learning system. Slow internet connectivity, network downtime and lack of computers were the main challenges encountered by teachers when using Elimika e-learning system.