As big data and data analytics have become an important issue in ad land, advertising agencies are facing various environmental changes. By conducting in-depth interviews with advertising experts, this study examines the experts’ perceptions about big data used in advertising industry. Then, it suggests the practical and professional implications in order for advertising agencies to strengthen the capability of data analytics. Advertising experts recognize that big data and data analytics are not only the basic and fundamental competence but also the problem of survival for advertising agencies in the age of digital media. They say that the issues faced by advertising agencies are the awareness of the need for obtaining and managing data, data silos and integration challenges, market uncertainty of the field of data analytics, and the difficulties in securing top talents dealing with big data and technologies. Experts suggest that advertising agencies preemptively should come up with a blueprint for data analytics to gain a competitive advantage. They emphasize that developing the organization of data analytics into a profit center within an agency and unrelenting investment in both people and infrastructure with a long term perspective are should be considered. More importantly, advertising agencies have to beware of the omnipotence of the analysis tool. It should be realized that the value of data analytics will be maximized when connecting the data analytics solutions or skills and domain experiences and knowledge of advertising experts.