To date, few online game-based learning studies have focused on developing children's growth creativity mindset (growth CM). This study, therefore, aimed to develop a game-based learning system to help children develop their growth CM. Additionally, we investigated the relationship between growth CM, hope belief, and creativity self-efficacy after game-based learning. Participants consisted of 132 fourth and fifth graders. With a pretest-posttest control group design, the experimental group completed a four-week intervention, whereas the control group received regular computer classes. Four types of creativity mindsets were identified: growth-internal, growth-external, fixed-internal, and fixed-external. The findings suggest that it is easier to overcome fixed CM than to enhance growth CM through game-based learning. Moreover, growth CM contributes to the development of hope belief and creativity self-efficacy, whereas fixed CM undermines hope belief and creativity self-efficacy in a game-based environment. Finally, hope belief is a mediator between growth CM and creativity self-efficacy. The findings of this study have implications for the design of a game-based learning system used to enhance growth CM, hope belief, and creativity self-efficacy.