Mindwandering (MW) is associated with both positive and negative outcomes. Among the latter, negative mood and negative cognitions have been reported. However, the underlying mechanisms linking mindwandering to negative mood and cognition are still unclear. We hypothesized that MW could either directly enhance negative thinking or indirectly heighten the accessibility of negative thoughts. In an undergraduate sample (n = 79) we measured emotional thoughts during the Sustained Attention on Response Task (SART) which induces MW, and accessibility of negative cognitions by means of the Scrambled Sentences Task (SST) after the task. We also measured depressive symptoms and rumination. Results show that in individuals with elevated levels of depressive symptoms MW during SART predicts higher accessibility of negative thoughts after the task, rather than negative thinking during the task. These findings contribute to our understanding of the underlying mechanisms of MW and provide insight into the relationship between task-involvement and affect.