In order to survive in the highly competitive internet business, companies have struggled to develop services which can satisfy users’ ever-changing needs and preferences. It is widely recognized that design plays a vital role in differentiating and upgrading the quality of products and product systems in the manufacturing sector. However, the actual role of designers in the rapidly growing internet business sector has remained an uncharted territory so far, even though designers have increasingly contributed to actualizing innovative solutions in new internet service development. This study explores how the role of designers in the internet service sector has progressed over the past decade. Both qualitative and quantitative research methods have been employed: (1) literature review and in-depth interviews with professional designers for tracking the historical progress of internet service design in South Korea since the mid-1990s and (2) two questionnaires given to digital design agencies and their clients to identify the designers’ actual role in internet business. We discovered that the role of designers in developing new internet services has changed in three distinctive steps over the past decade, i.e., from a passive to an active and finally to a strategic role. Along with these evolutionary changes of the designers’ role, a clear distinction between design services of digital design agencies and in-house design groups has been articulated. Digital design agencies have expanded their specialized design capacities for solving clients’ diverse design problems. On the other hand, in-house design groups have cultivated more strategic levels of design capabilities with long-term perspectives for their own internet service success.