Due to COVID-19 pandemic, online learning has been adopted. Without proper preparation, online learning has been forced to entirely substitute face-to-face/offline learning. As a result, the researcher recommended investigating students' perceptions of the implementation of online learning at SMA Negeri 8 Yogyakarta during the COVID-19 pandemic. In this research, there were two research questions: (1) How did the students of SMA Negeri 8 Yogyakarta perceive the implementation of online learning during COVID-19 pandemic? (2) What are the advantages and disadvantages of implementing online learning during COVID-19 pandemic for the students of SMA Negeri 8 Yogyakarta? Eleventh-grade students from SMA Negeri 8 Yogyakarta participated in the research. This study employed a mixed-method approach. The researcher used the theory of perception and online learning to answer the research questions. The data was collected using survey instruments in forms of a questionnaire and an interview. The findings proved that, in terms of technological aspects, the implementation of online learning has been a success. Reduced travel costs, increased learning autonomy and efficiency, as well as more access to higher-quality education were the advantages. Finally, there were some disadvantages, like distractions, time management, insufficient study time, and a reduction in self-motivation and enthusiasm in learning.