This study aims to examine the factors affecting customer loyalty in Sumbawa city, Nusa Tenggara Barat province, Indonesia. This province become the driving factor of the Islamic bank market because it is dominated by 97% Muslims. Meanwhile, the independent factors include profit sharing, service quality, transparency, and trust. Data were collected using a questionnaire and analyzed using multiple regression methods. The results showed that service quality, transparency, and trust positively affect the customer loyalty of Islamic bank, while profit sharing have no influence. Furthermore, Muslim financial institutions are expected to use their best performance to increase customer loyalty. The practitioners and regulators can improve their performance and develop the Islamic financial industry by considering the result above.