With the advances of technology, technological learning tools are becoming more important in enabling learners to study more effectively. The pre-requisite for the success of any technological learning tool hinges on its usability or technical ease of use. A tool that is not usable has the undesired effect of disrupting the user’s learning as more time is expended on learning the tool than the contents (Wong, Nguyen, Chang & Jayaratna, 2003). Therefore, the aim of this research is to explore and uncover the dimensions of the usability of the interactive e-study guide known as the iStudyGuide used as one of the main learning resources in the context of SIM University (UniSIM). Therefore, the research question in this study is “What are the dimensions that determine the usability of iStudyGuides?”. It employs a survey research methodology, utilising the statistical methods of exploratory and confirmation factor analysis. Data are collected from 278 students who used iStudyGuides in their learning at UniSIM. In the confirmatory factor analysis process, Bollen-Stine bootstrap p = 0.688. CFI = 0.996, RMSEA = 0.026 and PCLOSE= 0.918. The confirmatory factor analysis shows that the final model of usability of the iStudyGuides that comprises of the dimension of reliability, utility, learnability, accessibility and control has a good fit on the data. The emergence of the model of usability of iStudyGuides sets as the basis that iStudyGuides can be evaluated to ensure quality assurance in terms of usability.