The COVID-19 pandemic has forced higher education to enter into a phase of blended learning that combines in-person and mandatory online learning. This new combination has presented great challenges in promoting academic wellbeing. Anchored by the conservation of resources theory, this study undertakes to explore the contributions of personal resources to academic wellbeing. A total of 1934 undergraduates at a public university in China voluntarily participated in a survey during the 2022 spring semester. They were asked to rate their psychological capital (PsyCap) in general. They were also asked to rate their learning burnout, learning engagement, and academic buoyancy on the course level (namely through a course with English as a foreign language). Partial least squares structural equation modelling was used for the data analysis. The results confirm a direct positive association between PsyCap and students' learning engagement. In particular, the contribution of PsyCap to learning engagement is partially mediated by learning burnout. The moderation estimation reports that the positive effect of PsyCap on learning engagement is stronger for Chinese undergraduates with a higher academic buoyancy and that the negative link of learning burnout with either PsyCap or learning engagement is stronger for Chinese undergraduates with a lower academic buoyancy. This research is the first one to explore the beneficial joint roles of PsyCap and academic buoyancy in promoting academic wellbeing. The findings of this research offer novel and subtle insights into why and how PsyCap and academic buoyancy has contributed to easing learning burnout and boosting learning engagement in blended learning environments during the prolonged COVID-19 pandemic.