The goal was to determine the extent to which cognitive flexibility measured by category switching predicted unique variance in reading comprehension for elementary students after accounting for vocabulary and oral reading fluency. One hundred and one second through fifth grade students completed curriculum-based measures of reading comprehension and oral reading fluency, as well as vocabulary and cognitive flexibility (category switching) measures. As predicted, hierarchical linear regression showed that vocabulary and oral reading fluency were associated with reading comprehension, though only the association with oral reading fluency was significant. Importantly, cognitive flexibility (category switching) predicted unique variance after accounting for the other variables, demonstrating the relevance of category switching flexibility for reading comprehension. Exploratory analyses revealed that the unique role of cognitive flexibility was evident for older elementary students, but not for younger elementary students. These findings support the active view of reading, especially the importance of cognitive flexibility in supporting reading comprehension.