True conceptualization is critical in understanding the fundamental principles of general science at the primary level. Concepts developed without prior understanding of the subject are not always wrong, although they might be characterized as misconceptions. The current study was conducted to identify misconceptions in biology part of general science book. Furthermore, it was to analyze the most likely causes of these diagnose misconceptions among primary school students. The current study was a case study. Two-tier diagnostic tests and diagnostic test interviews were employed as study instruments. The 400 fifth-grade students were chosen on purpose as a test sample, and 20 students were chosen for the semi-structured interview that possessed more misconceptions. Thematic analysis was utilized to do a qualitative study of the data. In addition, data triangulation was performed to combine the test and interview results. Language misunderstanding, misinterpretation of prior knowledge and visualization inaccuracy were the main causes for diagnosed misconceptions. It was recommended that a suitable atmosphere for general science learning be provided and that teachers should design learning using the appropriate method, strategy, model, and media to dispel misconceptions in biology part of general science book among primary school students.