Problem-Based Learning (PBL), an instructional approach originated in medical education, has gained increasing attention in K-12 science education because of its emphasis on self-directed learning and real-world problem-solving. Yet few studies have examined how PBL can be adapted for kindergarten. In this study, we examined how a veteran kindergarten teacher, who was experienced with PBL in her own learning, adapted PBL to teach students earth materials, a topic emphasized in the new state curriculum standards but students had difficulty understanding. The pre-post tests showed that students improved their content understanding. Analysis of the classroom discourse showed that PBL and the teacher's facilitation strategies provided opportunities for students to develop their questioning skills. In conclusion, we discuss the implications of this study for using PBL in kindergarten classrooms.