Executive function is a fundamental component of the human cognitive architecture. Here, we investigate the rela-tionship between executive function and scientific reasoning. Eighth graders completed measures of three executive functions(EFs): shifting, inhibiting, and updating. They also completed a measure of cognitive flexibility, the Wisconsin Card Sort Task(WCST), that has predicted scientific reasoning in prior studies. Scientific reasoning was measured by a standardized test ofscience achievement. A principal components analysis found that the three EFs were separable. Different EFs predicted dif-ferent aspects of cognitive flexibility; notably, participants with poor shifting ability made more perseverative errors. Both EFand WCST predicted science achievement. Of note was the finding that better updating (i.e., working memory) was associatedwith higher science scores. These findings illuminate the role of EF in cognitive flexibility and scientific reasoning, and pointthe way to future studies of the effect of training EF on science achievement.