Provided are a computer program product, system, and method for allocating physical nodes for processes in an execution plan. An execution plan is generated indicating a plurality of processes. A resource requirement is generated indicating requested physical nodes and an assignment of the processes to execute on the requested physical nodes. A determination is made from the resource requirement of a resource allocation of physical nodes for the requested physical nodes and the processes. The execution plan is updated to generate an updated execution plan indicating the physical nodes on which the processes will execute according to the received resource allocation.