This study aimed to develop and implement a Scientific Environmental Project on the scarcity of water resources and to examine its impact on the environmental competency of elementary school students. The participants were 60 fourth-grade elementary school students, and pre- and post-tests were conducted. The collected data were analyzed using a paired samples t-test. The results indicated that elementary school students who participated in the Scientific Environmental Project showed significant differences in all sub-domains of environmental competency. Specifically, there were statistically significant differences in reflection and insight (p < .05), environmental information utilization (p < .001), creative problem solving (p < .05), environmental sensitivity (p < .05), communication and conflict resolution (p < .01), and environmental community competency (p < .001). These f indings suggest that the Scientific Environmental Project could be an effective instructional strategy for enhancing elementary school students’ comprehensive environmental competency. Furthermore, this study highlights the educational implication that environmental education in elementary schools may benefit from being and implemented in an interdisciplinary manner, particularly by integrating science education, in order to provide a meaningful contribution to sustainable education practices.