The increasing importance of relational marketing in the service sector as underlined by several authors and particularly by Berry (1983) culminates in a new marketing orientation toward internal marketing, even suggesting a significant impact of the latter on service quality perception. Several scholars argued that consumers attitude toward front-desk personnel often determines their attitude toward the service encounter as a whole (Berry and Parasuranam A., 1991), which evoke an evident role of employee’s customer orientation. This paper argues and then produces empirical evidence that customer orientation has a mediating effect between internal marketing and service quality perception based on a sample 116 banking customer advisors and 3 client of each (348 client). To do so, an internal marketing performance measurement scale has been established according to Churchill’s paradigm. Two dimensions were found significantly reliable and valid: gratitude-Empathy and Integration-support. And only the first one was found to have a significant impact on customer orientation.