The demands of an increasingly knowledge-based society and the dramatic advances in mobile phone technology are combining to spur the growth of mobile learning (mLearning). However, for mLearning to attain its full potential, it is essential to develop pedagogy and instructional design tailored to the needs of this new learning environment. At present, there is a lack of research on message design for mLearning. Towards these ends, this paper explores the principles and processes of message design for mLearning, including the influence of learning and cognitive theories, human-computer interaction principles, devices and methodologies. And it presents a number of practical guidelines for designing instructional messages for mLearning. (Contains 2 tables and 1 figure.)