A system for providing an interactive broadcast service and method thereof are disclosed, by which a communication service and an interactive broadcast service can be unitedly supported in an IMS (Internet protocol Multimedia Subsystem) environment. The present invention includes a first server receiving a message of the protocol from the UE and making a registration for a service subscription for the UE from subscription-related information included in the message, a first media server receiving a multimedia stream of the broadcast service to be transmitted to the registered UE from a corresponding broadcasting network, and a second media server connected to the broadcasting network, converting interaction data inserted in the message of the protocol received from the UE to a signal format supported by the broadcasting network.