Successful operations of Islamic banks have made the Islamic banking system popular in all societies now more than ever. There is an increased interest in adopting Islamic banking principles by conventional banks. One of the visible consequences of this realization is the opening of Islamic windows by conventional banks. At present, there are 25 Islamic windows by conventional banks in Bangladesh and the number is increasing every year. The role of Islamic banking windows has not been critically evaluated thus far by any researcher. As observed, there are a number of challenges for the smooth functioning of these windows. Questions arise: are the Islamic windows fully separated from the conventional part? How far are the operations of these windows in strict compliance with Shariah requirements? As such, the study aims at evaluating the role, finding out the major challenges, and assessing the Shariah compliance of Islamic banking windows by conventional banks in the context of Bangladesh. A semi-structured questionnaire is used to interview selected bankers as well as Islamic scholars. Respondents are selected based on purposive sampling. This study reveals the actual role and potential challenges in the operation of Islamic windows. Some policy recommendations are suggested for the sustainable development of Islamic banking windows in Bangladesh.