Reports from the advertising industry suggest that the pressure to create effective integrated campaigns across the ever-increasing mix of paid, owned and earned media is putting an enormous strain on client/agency relationships. This research identifies the main challenges that an Integrated Marketing Communication (IMC) approach places on this relationship and thereby advances the IMC literature by examining the practical challenges of implementation. Six key issues, developed from academic and industry sources, are presented to advertising experts, through a Delphi study, to stimulate debate and identify areas of agreement. The findings are brought together in a model which presents three main areas that need to be addressed, along with specific recommendations. These topics include the need for clients to provide stronger leadership in defining agency roles and responsibilities, more transparent remuneration systems to encourage teamwork across agencies as well as individual input and an increased emphasis on the strategic contribution from agencies.