Sleep deprivation can result in degradation of sustained attention through increased distraction by task-irrelevant exogenous stimuli. However, attentional failures in the sleep-deprived state could also be a result of task-unrelated thoughts (TUTs, or mind wandering). Here, well-rested and sleep-deprived participants performed a visual search task under high and low perceptual load conditions. Thought probes were administered at irregular intervals to gauge the frequency of TUTs and level of meta-awareness of mind wandering. Despite sleep-deprived participants reporting more TUTs, they also reported less awareness of TUTs. Although the frequency of TUTs decreased in the high load condition in well-rested participants, they were equally frequent across low and high perceptual load conditions in sleep-deprived participants. Together, these findings suggest that sleep deprivation can result in a loss of ability to allocate attentional resources according to task demands consistent with diminished executive control. This may have been exacerbated by reduced meta-awareness.