A digital broadcasting system and a method of processing data are disclosed. Herein, additional encoding is performed on mobile service data, which are then transmitted, thereby providing robustness in the processed mobile service data, so that the mobile service data can respond more strongly against fast and frequent channel changes. The method of processing data in a transmitting system includes receiving mobile service data, encapsulating the received mobile service data to a transport stream (TS) packet, and outputting the encapsulated mobile service data as a mobile service data packet, and multiplexing a main service data packet including main service data and the encapsulated mobile service data packet, thereby transmitting the multiplexed data packets to at least one transmitter located in a remote site.