Hi @Kara_Jacobson and welcome to the forum!
Yes, you can definitely make a subtask dependent on another subtask.
One thing you have to remember is that by default, subtasks do not inherit an association to their parent task’s project (you have to manually make that association if you choose to).
This leads to a catch with creating subtask dependencies - as noted above in this thread, when Asana displays the list of tasks to choose from to identify the dependency task, it displays subtasks in the format of
Subtask name < Parent task name
The problem becomes if you have multiple subtasks and parent tasks with the same name (as in, for example, the same task/subtask structure in multiple different projects). In that case, it’s impossible to know which subtask to choose.
The two ways to resolve this issue are to either make sure all of your parent tasks and subtasks have unique names, or to assign the subtasks to their parent’s project (if you do this, the project name is added to the Subtask name < Parent task name display.
I realize the above may be confusing so don’t hesitate to ask any follow-up questions!