For this paper, an educational computer game called Ecoship Endeavour was designed based on the guidelines of the inquiry, communication, mystery, decision making, challenge, and rewards (ICMDCR) framework to help facilitate critical thinking skills in students. To examine the effectiveness of the proposed digital game-based learning (DGBL) approach, a quasi-experiment was conducted in the units of “food relationship among living things”, “life processes in plants”, and “energy” of an elementary science course. A total of 127 fifth grade students (females only) from four classes consented to participate in this learning activity. Two classes ($N = 62$ ) were assigned to the experimental group and guided by the developed game, and the other two classes ($N = 65$ ) were allocated to the control group and taught by the conventional method of science teaching. The experimental results revealed that Ecoship Endeavour significantly improved the critical thinking skills of students; however, it was also revealed that the DGBL activity had no significant effects on students' learning motivation and self-efficacy for science learning. Finally, more research is needed to examine the instructional benefits of the proposed method with more inclusive research samples consisting of both male and female learners. The outcome of this research may help researchers, teachers, and practitioners in the educational sector to evaluate the effectiveness of serious games in facilitating students' critical thinking.