In the task-switching paradigm, the most prominent measure are the switch costs indicating worse performance on task switches compared to task repetitions. Previous research showed that introspective RT estimations capture the switch costs. However, the meaning of these introspective switch costs is not yet well understood. They may simply reflect the immediate experience of an executed response or rely on abstract theory-based knowledge about task transitions (“task switches are difficult and take longer”). The present study investigated how introspective judgments are formed during task switching. In Experiment 1, we tested participants' awareness of task transitions as a prerequisite of theory-based knowledge. On a random subset of trials, participants had to indicate whether the current task repeated or switched relative to the previous trial. Judgments were collected with a short (1000 ms) and a long (5000 ms) time window to distinguish intuitive from deliberate decisions. As predicted, participants reliably recognized the transition even with a short time window. In Experiment 2, we reduced immediate experience-based knowledge by introducing NoGo trials where participants had to refrain from responding. Hence, required RT estimations most likely relied on theory-based processes. The results showed introspective switch costs even in NoGo trials suggesting that participants may use theory-based knowledge to inform their judgments although experience-based influences of covert responses may also play a role. Taken together, our findings provide novel insights into introspection during task switching contributing to a better understanding of how task-switching performance may relate to decision-making.