This study implemented a three-stage problem-based estimation instruction scenario and combined it with mobile technology to provide elementary teachers with an effective e-tool for observing student estimation and leading effective class or group discussions on the selection and assessment of appropriate strategies for solving daily estimation problems. Twenty-eight fourth graders were randomly sampled and assigned to two groups: the experimental group (problem-based estimation instruction using mobile devices) and the control group (problem-based estimation instruction without mobile devices). The analytical results demonstrated that problem-based estimation instruction could effectively help students learn computational estimation skills. Moreover, using mobile devices for problem-based computational estimation instruction appeared to help students discuss and cooperate with others, and moreover the mobile-device-supported problem-based estimation scenario helped students develop metacognition knowledge of estimation strategies. (Contains 1 table and 9 figures.)