With the development of data-intensive internet services, the world has witnessed explosive growth in mobile data consumption during the last couple of years. The upcoming generation of 5G-capable phones and networks will continue and even accelerate that process. At the same time, consumers are becoming more conscious about their data consumption because their monthly caps of mobile data plans can be easily exhausted by premium content, such as high-definition videos and virtual-reality games. In response, the mobile network operators (MNOs) have proposed a new business model, the so-called sponsored data plans, to subsidize consumers by transferring at least part of the data bills from consumers to content providers. Although industry practitioners claim that sponsored data plans increase consumer welfare, our analysis reveals that the impact of sponsored data on consumer surplus depends crucially on whether the MNO has complete information of the consumers’ valuation of mobile data. Our analysis helps provide a clearer picture of the impact of sponsored data on consumer surplus while reconciling the conflicting views from scholars, digital rights groups, and the network carriers.