The purpose of this paper is to identify the key dimensions of service quality of an Islamic bank. A modified SERVQUAL scale based on five dimensional approach is administered to determine the perception of Islamic banks customers towards service quality. The basic purpose of the study is to develop a scale for this purpose. A mail survey with the help of online questionnaire is carried out. Non probability sampling especially snowball and judgmental sampling techniques for sample size 185 has been used. The responses were collected from the 7 Islamic banks located in the Gulf countries mainly the U.A.E. and the K.S.A. Data analysis is done in the form principal Component Analysis (PCA) and Confirmatory Factor Analysis (CFA) to validate the scale. Independent sample T test and One Way ANOVA are used to validate the hypotheses. Results from structural equation modeling (SEM) of relationship between multidimensional service quality scale and one-dimensional customer satisfaction are validated. By the ANOVA results, the differences in the service quality dimensions of the banks with respect to demographic variables, has also been ascertained.