Citizen science is a promising field for research in climate change. It has also been recognised with great potential in the field of climate change education, especially in the increase of scientific knowledge and science process skills. The study aims to examine the contributions of citizen science to learning outcomes regarding climate change and the development of science skills. A mixed-methods approach involving a pretest, posttest, records inserted in the iNaturalist platform, semi-structured interviews with the researchers, and a questionnaire to iNaturalist users that validated the observations inserted by students, were applied to access students' knowledge and development of science skills. Findings showed an improvement in scientific knowledge related to consequences of climate change, species identification and students' development of science skills, such as observation, data collection and teamwork. Indeed, this study supports that students can be involved in all stages of scientific research and the data can be used in scientific investigations, improving the size and quality of citizen science databases. This investigation reinforces the importance of citizen science projects in a school context to improve the student's skills and scientific knowledge regarding climate change.