The quality of education is important and selecting appropriate teaching learning process promotes students’ performance, hence, the main purpose of this study was to investigate the effectiveness of 5Elearning cycle-based instruction on 9th-grade students’ conceptual understanding of the Circulatory system in Tana Hique high school Bahir Dar town. This study was grounded on Piaget’s theory of cognitive functioning development and 5e learning related theories. A quasi-experimental research design was employed. Out of 15 grade nine sections (N=938, F=519 and M=419), two sections (N=131, F=70 and M=61)) were selected randomly and assigned as experimental (N=65 (F=34 and M=31) and control (N=66, F=36 and M=30) groups. The students in the experimental group were instructed with the 5E learning-based instruction, whereas the students in the control group were instructed with traditional based instruction for two weeks, to teach circulatory system related topics from grade nine biology textbook, based Ethiopian curriculum. Circulatory system conceptual understanding Test (CSCUT) which was administered before and after treatment as pre and posttest respectively and classroom observation was used as data collection instruments. Pretest and posttest were analyzed quantitatively (descriptive statistics and t-tests), while classroom observation assessments were analyzed qualitatively. The result of this study (pre and post-test) indicated that 5E LCBI showed a significantly superior effect over TBI for improving students’ conceptual understanding of circulatory system-related concepts and discarding alternative conceptions. The classroom observation results supported these findings. From the results, it is possible to conclude that the 5E learning cycle-based instruction has more effective than the traditional-based instruction when it comes to students’ conceptual understanding of circulatory system-related concepts. Based on the finding, the researcher suggested that curriculum developers should incorporate the constructivist strategy of the 5E learning cycle model into the biology curriculum as an instructional model for teaching biology.