By adopting a relational approach based on customers, Islamic banks like all service companies aim to guarantee and improve satisfaction through the perfection of the quality of service in order to retain current customers, to attract them. new potentials, but above all to promote the relationship with them. This is more important for those institutions which can only rely on the perceived quality of service to face the competition. The primary objective of this article is to identify the effect of quality of service on customer loyalty behavior towards their banks. A quantitative study was carried out in 2019 with 356 clients of 6 Islamic banks in Mauritania. The results of data analysis using structural equation modeling show that service quality has a positive impact on customer satisfaction, but it has no effect on trust and loyalty. On the other hand, satisfaction accredits, appreciably, trust just as it considerably strengthens customer loyalty.