The purpose of this study is to develop a mindfulness-based emotional ability improvement program targeting upper-grade elementary school students and test whether it is effective in their emotional recognition and expression, behavioral problems, and mindfulness. The summary of what was done in this study is as follows. First, by reviewing foreign programs with the theoretical background of mindfulness and social emotional learning, we developed a mindfulness-based emotional ability improvement program for a total of 8 sessions. Second, in order to verify the effectiveness of the developed program, a mindfulness-based emotional ability improvement program was administered to the experimental group targeting 5th and 6th grade elementary school children, but not to the control group. Third, pre- and post-program tests were conducted on the experimental and control groups, and the results were compared and analyzed. As a result, the mindfulness-based emotional ability improvement program was effective in emotional recognition and expression in upper elementary school students. It was effective in reducing physical symptoms, social immaturity, and attention problems among behavioral problems. However, it was found to be ineffective for mindfulness. Based on these research results, the significance and limitations of the study and future research directions were discussed.