Theories have shown that using internal marketing could be beneficial for the duration of a company; indeed, by responding to the needs of their employees, companies manage to keep them involved and enhance their perceived efficiency. The purpose of this dissertation is to determine if the theory is applicable in a particular case or if it is just that, a theory. In order to do so, the research examined the application of an internal marketing strategy in a French clothing retailer and looked for ways to increase sales-assistants’ perceived efficiency thanks to those actions. Nature / Scope: the nature of this research is explanatory; that is to say, it aimed at studying a particular case so as to draw out more general conclusions. In order to do so, an analysis of the existing literature was undertaken so as to find as much articles as possible on the topics related to internal marketing and an analysis of a particular case was conducted. Method: Regarding the adoption of the case study strategy, two methods were used: a qualitative and a quantitative research that aimed at determining how the theories are applied in practice. Contributions: The research contributes to the literature as it fills a gap related to the application of internal marketing in France, and more precisely in clothing retail businesses. Plus, it brings a new theory under which the fact of setting-up an internal marketing mix is major for employees’ involvement in a company and the duration of this company.