This research is concerned with the utilization of mobile devices as a tool for learning (m-learning). Therefore, approaches in developing learning applications that can suit the small screen size and restrictive capabilities of the devices are studied so that they can help the learners in understanding the concepts being delivered from the applications. This paper presents the study of design principles and requirements for the m-learning application development. The study covers the suitable architecture, learning theories and modules that are appropriate for an application developed for the platform. Based on the results of the study, one m-learning course content prototype is developed. Hence, this paper provides some discussions regarding the guidelines utilized in developing the prototype. Finally, usability testing had been conducted among 66 System Analysis and Design (SAD) course students in evaluating the usability level of the developed prototype. The results showed that majority of the students agreed that the developed MOSAD application has met the requirement of usability element. ©2010 IEEE.