Exploring science teachers' classroom assessment behaviors is a way to understand the professional knowledge competencies underlying effective teaching practices. One of the most important components of in-class assessments is teacher questions. However, studies examining teacher questions that provide support to accurately determine student learning and manage the lesson effectively are quite limited. This research presents a case study of a science teacher in Turkey regarding the question types and questioning proficiency in the teaching of 5th grade "Measurement of Force and Friction" and "Matter and Change". The data have been collected through course observations. The study used an observation evaluation protocol to analyze the video recordings taken from the science teacher's lectures. The results of this study showed that about half of the questions that the science teacher has asked in his class remain at a partially appropriate and inappropriate level, and that the teacher mostly prefers questions that aim to evaluate real information and summarize what is important in his courses. These results point to the need for professional development on a teacher's questioning practices. Therefore, it can be said that those who plan professional development programs for science teachers should consider efforts to improve teacher questioning practices. Keywords: case study, classroom observation, science questions, science teacher questioning