The study aims to measure the customers’ expectation levels of service quality in the food retail sector against their perceptions levels of the service quality at Nakumatt hypermarkets and to determine the gap between customers’ expectations and their perceptions of the service quality. A descriptive research design was adopted to carry out the research. Using a SERVQUAL survey instrument based on the Dabholkar RSQS model this study was conducted with customers from Nakumatt stores in Nairobi Kenya. . Through a self reported questionnaire, 150 respondents were approached using a convenience sampling method from the store locations. Key findings include confirmation that customers have higher expectations for service quality in retail supermarkets than is anticipated. Gap 5, which is a gap between customers’ Expected Service and customers’ Perceive This study does not differentiate applicability of the RSQS in the different formats of the retail store. Future research should examine the impact of the different retail formats in using the scale for measuring retail service quality. Also the customers were a little reluctant in revealing the information because of the lengthiness of the questionnaire. This is one of the few studies which attempted to investigate customers’ expectations of service quality in retail supermarket in Kenya. d Service, was identified.