The most critical element in the real-time operation of RFID application programs that are suitable for the mobile environment is the RFID middleware, made exclusively for mobile handsets, which processes collected data on a real-time basis and sends only the useful information to the application client. In this paper, we intend to design and implement a mobile RFID middleware system that supports the mobile handset environment for real-time based processing of the necessary data in the mobile environment. The proposed mobile RFID middleware system includes a mobile reader interface that collects the tag data, a mobile filtering engine that processes the tag data into more meaningful data that is sent to the application interface, and finally the mobile application interface that supports the m-SOAP application access protocol for interfacing with existing mobile applications. The filtering speed of the newly-developed middleware engine was found to be suitable for the characteristics of mobile handsets.