A system and method can support dynamically scaling up/down transactional resources in a transactional middleware machine environment. Transactional resources, such as groups and machines, can be by added or removed using a dynamic resource broker according to resource usage changes. The transactional middleware machine environment can comprise a deployment center in the transactional middleware machine environment, wherein the deployment center maintains one or more deployment policies for the transactional middleware machine environment and one or more deployment agents. Each of the one or more deployment agents is associated with a transactional middleware machine of a plurality of transactional middleware machines in a transactional domain in the transactional middleware machine environment. The deployment center operates to receive machine usage information from the one or more deployment agents, and dynamically scale up/down resources used in the transactional domain based on the resource usage information collected by the one or more deployment agents.