This study aimed to investigate the effect of an online science course on the academic achievement of a fifth grade "World of Living" unit, which was carried out using the materials created with web 2.0 tools, as well as to determine the students' opinions about the application. This study consisted of a total of 120 fifth grade students studying in state schools in Istanbul during the academic year of 2020-2021. In determining the study group, purposeful sampling methods were used. In the experimental group (n = 60), the course was taught with web 2.0 supported materials; in the control group (n = 60), instruction was made by adhering to the activities in the textbook. The research was carried out by making use of mixed method research. A quantitative quasi-experimental model with pre- and post-test control groups was used. In the qualitative dimension, opinions were obtained from the students after the application. In the study, semi-structured interview form and academic achievement test prepared for the unit of the world of living things were used as data collection tools. While the data obtained from the students to the achievement test before and after the application was transferred to a statistical package program and analyzed; the data obtained from the interview form were analyzed using content analysis. When the post-test academic achievement score data obtained from the students were compared as a result of the study, it was found that there was a significant difference in favor of the experimental group. In addition, result from the interviews, revealed that students found science teaching with web-supported materials fun and enjoyable and that they wanted these to be used in science lessons. As a result of this study, it is recommended that web 2.0 tools be used by educators in science education.