Pre-service science teachers' conceptual understanding of astronomical concepts and their misconceptions in these concepts is crucial to study since they will teach these subjects in middle schools after becoming teachers. This study aimed to explore both seventh-grade students' and the science teachers' understanding of astronomical concepts and to diagnose the misconceptions of seventh-grade students and pre-service science teachers regarding some basic astronomy concepts derived from a three-tier test. The test was administered to 105 pre-service science teachers and 91 seventh-grade students. The best conceptual understanding was related to the properties of the Sun. The students and pre-service science teachers have some common misconceptions in astronomy. Pre-service teachers mostly have misconceptions not regarding complex concepts but instead in very basic knowledge of astronomy. There is a need to take serious measures to correct the misconceptions of the teachers, since under such circumstances it is optimistic to expect them to teach the subject correctly.