Abstract: Disclosed herein are vascular access systems with dilator locking mechanisms, and associated devices and methods. In some embodiments, the dilator locking mechanisms include a first cap coupled to a dilator component and a second cap coupled to the vascular access system. The first cap can include one or more locking members. The second cap can include one or more locking features, each configured to be releasably coupled to one of the locking members. In operation, the dilator component can be inserted into the vascular access system, and at least a portion of one or more of the locking members can be aligned with and inserted into the corresponding locking feature to, e.g., couple the first cap and the second cap. The interaction between first and second caps when coupled can at least partially prevent the dilator from moving relative to the vascular access system.