Students always suffer from burnout during online learning. Although social support and cognitive engagement are associated with learning burnout, limited information is available on whether and how these relationships change over time in an online learning setting. This study investigated the longitudinal relationships between social support, cognitive engagement, and learning burnout and the further relations associated with performance. Forum data and self-reported data from 116 online college students were analyzed at two different timepoints. We found received social support is not related to learning burnout but shows a positive relationship with cognitive engagement that increases over time. Perceived social support is always positively correlated with cognitive engagement and negatively associated with learning burnout. Cognitive engagement has a negative relation with learning burnout that increases over time. Moreover, the negative relationship between learning burnout and performance emerges in the middle of the term but not at the end, thus indicating a significant change over time. The findings have significant ramifications for both preventing and intervening in online learning burnout.