This chapter presents a study that examined the effects of prior knowledge and multimedia design on developing mathematical conceptual understanding in a mobile learning environment. Two different approaches—instructional and noninstructional—were used in the design of the multimedia representation to facilitate students learning for a more complete understanding. Seventy students with different levels of prior knowledge in a secondary school participated in the experiment. Participants were assigned to the 2 (high vs. low prior knowledge group) × 2 (instructional vs. noninstructional) factorial groups to receive the 100-min treatment. The results revealed that the low prior knowledge group outperformed the high prior knowledge group in conceptual knowledge of low order thinking; the instructional group outperformed than the noninstructional group in conceptual knowledge of high order thinking and procedural knowledge; and there was no interaction of prior knowledge and design approach. These findings suggest that mobile multimedia environment enhancing viewing is sufficient for the low order thinking skill development, but not for the high order in mathematics concept learning and procedural skill. Finally, recommendations for future research were suggested.