Background: Traditional face-to-face instruction swiftly transitioned into online learning during the global COVID-19 outbreak. Students' experiences and academic performance in this new learning platform need evaluation. Purpose: The purpose of this research was to determine the undergraduate nursing students' stress, satisfaction, and academic performance during online learning. Methods: This research was considered a cross-sectional and descriptive-correlational study. The research participants were the second-year undergraduate nursing students from one nursing school in the Philippines. The data were collected using a web-based survey questionnaire and then analyzed using descriptive statistics and Spearman's rho correlation. Results: The results revealed that the undergraduate nursing students considered having online learning during the COVID-19 outbreak to be stressful (44.4%) and very stressful (47.2%). Moreover, the undergraduate nursing students had low satisfaction (37%) and moderate satisfaction (46.3%) having the online learning during the COVID-19 outbreak. The undergraduate nursing students' academic performance were affected by the COVID-19 pandemic and resulted in poor (37%) to fair (50%) academic performance and were considerably (43.6%) and greatly (30.6%) affected by the pandemic. Online learning stress had a significant and inverse correlation with online learning satisfaction (p=0.000) and academic performance (p=0.012). Conclusion: Stress negatively impacts the undergraduate nursing students' satisfaction and academic performance. This research suggests that certain measures should be performed to reduce stress and improve the online teaching-learning processes during the COVID-19 outbreak.