This study examined how to foster pupils' mathematical communication abilities by using tablet PCs. Students were encouraged to generate math creations (including mathematical representation, solution, and solution explanation of word problems) as their teaching materials and reciprocally tutor classmates to increase opportunities for mathematical communication during a semester. A reciprocal peer-tutoring-enhanced mathematical communication system was designed for supporting students' math creations and reciprocal peer-tutoring activities. An experiment involving 51 second-graders was conducted to evaluate their improvement in mathematical communication abilities. While the control group received one-to-one self-learning mathematical materials and teacher-led instruction, the experimental group was engaged in computer-supported reciprocal peer tutoring in the same environment with the same materials. Both groups were evaluated by using a mathematical communication ability assessment. The result indicated that the experimental group outperformed the control group in the assessment. Additionally, math creations were analyzed for assessing students' formative development. The results showed that students' math creations became clearer and more efficient. In other words, their mathematical representations and solution explanations became more accurate after the learning activity.