In accordance with an embodiment, described herein is a system and method for providing multitenancy support in a platform as a service or cloud computing environment. A platform component enables a service runtime to be shared by multiple tenants, by providing each tenant with a dedicated share or slice of a runtime instance. Each share/slice can be isolated from other shares/slices with respect to factors such as, for example, configuration, or quality of service. In accordance with an embodiment, during provisioning of a particular service runtime, a runtime definition associated with the service runtime can be utilized, for example by a service management engine, to configure the platform component to install one or more services within the service runtime. A particular service and its service runtimes can also be provisioned, within one or more runtime pools, according to a service runtime definition and placement configuration.