Authors: M. Nur Rianto Al Arif, M. Arief Mufraini, M. Agung Prabowo Abstract: After the enactment of Law 21 in 2008 that stated about the spin-off of Islamic banking units, some Islamic business units had done the spin-off. This led to an increase in the number of full-fledged Islamic banks. This study examines the relationship among spin-offs, market structure, and efficiency in the Islamic banking industry. We find a difference in efficiency between spin-off banks and non-spin-off banks. The increasing number of full-fledged Islamic banks does not mean that performance (measured by efficiency) will increase. These results show the opposite result with the goal of spin-off policy, which is to enhance the performance of Islamic banks. KEY WORDS: efficiency, Islamic banks, market structure, spin-off JEL CLASSIFICATION: G21, G39, L11 Source: https://www.tandfonline.com/doi/full/10.1080/1540496X.2018.1553162