Multitasking is ubiquitous in everyday life, which means there is value in developing measures that predict successful multitasking performance. In a large sample (N = 404 contributing data), we examined the predictive and incremental validity of placekeeping, which is the ability to perform a sequence of operations in a certain order without omissions or repetitions. In the context of multitasking, placekeeping should play a role in the performance of procedural subtasks and the interleaving of subtasks that interrupt each other. Regression analyses revealed that placekeeping ability accounted for 11% of the variance in multitasking performance, and had incremental validity relative to each of a diverse set of cognitive abilities (working memory capacity, fluid intelligence, perceptual speed, and crystallized intelligence). The predictive validity of placekeeping for multitasking was stable across samples of performance and robust to placekeeping practice. Broader measures of performance on our placekeeping task accounted for 21% of the variance in multitasking performance and had incremental validity relative to an estimate of psychometric g. The results provide evidence that placekeeping is a distinct cognitive ability with its own specific role to play in multitasking, and raise the possibility that measures of placekeeping ability could have utility in selecting personnel for occupations that require certain kinds of multitasking, such as interleaving of procedures.