Learning Management System is a software-based technology that is widely adopted by universities. While the implementation of LMS has been successful in developed countries, the utilisation of LMS in developing countries is still considered low. It is believed that there are some barriers that may influence the use of LMS which include Technical Support, Instructional Design and Self-Efficacy. The present research aims at examining the influence of these factors on students' use of LMS. Thus, a research model will be developed based on extending Technology Acceptance Model (TAM). Using the Stratified Random Sampling (SRS), 400 students were selected from three Saudi universities. The participants completed the survey questionnaire that measures their responses to the seven constructs. The data was analysed using Structural Equation Modelling by AMOS. The results showed that the three proposed external factors including technical support, instructional design and perceived self-efficacy had a significant influence on students' use of LMS. These factors had significant direct effects on both perceived ease of use and perceived usefulness of LMS. The results confirmed the validity of the extended TAM model in determining users' usage of LMS. The study also addressed several significant implications for the practitioners and researchers in the field.