Background: Corona virus disease (COVID-19) has completely changed the learning environment and experiences of adolescent learners. Aim: This study aimed to determine adolescents' perceptions and academic stress towards online learning during COVID-19 pandemic. Design: The study was quantitative research utilizing the descriptive survey design. Sample: The study participants were one thousand one hundred (1,100) adolescents from eighteen preparatory and secondary schools in Minia City, Egypt. Tools: Four tools were used in this study: Tool I: Profile characteristics of the studied adolescent .Tool II: Methods of online learning. Tool III:Online learning perception scale. Tool IV:Educational stress scale. Results: The study revealed that participants were mostly females, 16-18 years old, and in grade 12. Adolescents had a moderate level of perceptions towards online learning and a high level of academic stress during the COVID-19 pandemic .There was a significant relationship between the perceptions of adolescents towards online learning and academic stress during the COVID-19 pandemic. Conclusion: Adolescents taking online classes during the COVID-19 pandemic experienced academic stress which was strongly related to their perceptions towards online learning. Recommendation: Future researchers may explore different compounding variables contributing to academic stress and perceptions during outbreaks.