This study aims to assess primary school teachers' knowledge of basic astronomy concepts, such as the sizes and shapes of, and the distances between, the Sun, the Earth, and the Moon, lunar and solar eclipses, and the motions of the Moon and the Earth. Out of a total of 1,533 teachers, 398 (26%) were reached and asked to take a knowledge test. On the knowledge test, the overall performance of the teachers, whose task it is to teach the astronomy concepts in the fifth grade Science and Technology curriculum, stands at 70% while the students' success rate is approximately 50%. It is noteworthy that approximately one out of every three teachers answered the questions incorrectly. In this study, the primary school teachers' low performance on the same questions as the students can be observed as an indicator of this. Placing an astronomy course in undergraduate level in the elementary school teacher-training program could be useful. Thus, pre-service teachers have enough knowledge regarding astronomy subjects before starting their careers.