Provided are a computer program product, system, and method for determining storage tiers for placement of data sets during execution of tasks in a workflow. A representation of a workflow execution pattern of tasks for a job indicates a dependency of the tasks and data sets operated on by the tasks. A determination is made of an assignment of the data sets for the tasks to a plurality of the storage tiers based on the dependency of the tasks indicated in the workflow execution pattern. A moving is scheduled of a subject data set of the data sets operated on by a subject task of the tasks that is subject to an event to an assigned storage tier indicated in the assignment for the subject task subject. The moving of the data set is scheduled to be performed in response to the event with respect to the subject task.