Presidents select from a range of instruments when creating new policies through executive action. We study strategic substitution in this context and argue that presidents use less visible means of unilateral instruments when Congress is likely to scrutinize presidential action. Using data on unilateral orders issued between 1946 and 2020, we report two main findings. First, analyzing presidents’ choice of instruments, we show that presidents are more likely to substitute memoranda and other less visible instruments for executive orders and proclamations during periods of divided government. Second, after accounting for the substitution of executive orders with other instruments, we find that presidents issue greater numbers of directives during divided government than during unified government. These findings provide new evidence about the limitations of the separation of powers as a constraint on presidential unilateralism and highlight the importance of accounting for the variety of instruments through which presidents create unilateral policies.