The aim of this research is to examine the effects of web 2.0 tools used in online astronomy education on the conceptual achievement of 5th grade secondary school students. For this purpose, the Sun, Earth and Moon unit was processed online using web 2.0 tools. The study was implemented in a public secondary school over a period of 6 weeks. Mixed research method, which combines qualitative and quantitative research methods, was used in the study. An easily accessible sample model was used to determine the study group. The sample of the study consists of 12 students (7 girls, 5 boys) in the 10-11 age group. The "Sun, Earth and Moon Achievement Test" developed by Sontay & Karamustafaoglu (2020) was used as a quantitative data collection tool in the study. Qualitative data collection tool "Semi-Structured Telephone Interview on the Concepts of the Sun, Earth and Moon" was used. SPSS program was used in the analysis of quantitative data. Content analysis method was used in the analysis of qualitative data. As a result of the study, it was seen that online education supported by web 2.0 tools within the scope of the Sun, Earth and Moon unit had a positive effect on students' conceptual success.