The Covid-19 pandemic has struck all parts of the world with huge impacts on all fields, including education. The education sector needs innovative learning media to adapt to the impact of this pandemic. The objective is to develop an Adobe Flash-based interactive multimedia of plane geometry that is feasible and effective as an answer to media innovation. This is categorized as developmental research using the Analysis, Design, Development, Implementation, and Evaluation (ADDIE) model. The subjects included 3rd-semester students of Elementary Teacher Education/Pendidikan Guru Sekolah Dasar (PGSD), the academic year of 2020/2021. The feasibility of Adobe flash-based media was assessed by media experts and content experts, while the effectiveness data were obtained from student learning evaluations. The results showed that Adobe Flash-based interactive multimedia of plane geometry scored 89.17% and categorized as ‘very feasible’ seen from the media aspect while from the content aspect, it scored 87%. Different learning outcomes were found before and after using the established media, which were 67.92 and 76.39 respectively. The significance test showed that the t-value = 6.353, greater than the t-table df (35) = 2.032, p <0.05. These results concluded that Adobe Flash-based learning media of plane geometry is feasible and effective in improving PGSD students’ mathematics learning outcomes.