information technology (IT) in order to take advantage of the potential of data for business objectives. While users have received attention in many ways, we note that the capability literature has focused more on the IT supply side. We argue that user capabilities have moved to an integral position in firm competitive advantage, and call them “User IT Capabilities” (UIC). A survey was conducted to collect data from Japanese organizations, and a total valid sample of 1,170 respondents involved in big data use was extracted. The findings show the effect of UIC on the performance of big data analytics and firm competitiveness, mediated by the variable of organized big data analytics (OBDA). The direct effects are shown to be valid irrespective of company size, although the levels of UIC and OBDA are higher in larger firms.