Expert blogs have become an important source from which consumers obtain information about products and brands. Consumers heed information from such blogs because they are provided by fellow consumers who are regarded as experts and yet are not restrained to speak for a particular company. Thus, expert blogs are considered more credible, and it is likely that when expert bloggers choose to write favorably about a brand, consumer perception about the brand is enhanced. Furthermore, expert blogs may influence not only consumer perception of a focal brand, but also that of competing brand. By analyzing a novel, comprehensive dataset that combined expert blog sentiment of competing brands in the PC industry and consumer perception of the brands at a daily level, our study unveils three insights: 1) expert blog sentiment on a focal brand is positively related to consumer perception about the brand while negatively related to that of its competitors; 2) the focal brand’s blog sentiment has a reinforcing relationship with its future blog sentiments, while a cannibalistic relationship with that of its competitors; and 3) the extents of the positive and reinforcing relationships depend on the firms’ position (leading vs. non-leading). Implications for research and practice are discussed.