To understand how learner metacognition and goal orientation affect learner problem-solving in a Serious Game (SG) environment, this study examined 12 undergraduate students' metacognition, goal orientations, and problem-solving performances and processes while playing a SG that adopts problem-based learning pedagogy to teach space science. Utilizing survey responses, computer log data and stimulated interview recall in a laboratory setting, this study finds that cognitive bias and problem complexity combined with learner characteristics can affect learner problem-solving. The authors also summarize 10 operational steps for successfully solving problems in this SG. The findings offer insights on how learner characteristics impact problem-solving. It also contributes to the understanding of designing SG environments to benefit learners based on their metacognitive levels.