Purpose While the Noble Quran dictates the prohibition of interest, conventional banks promote Islamic banking by opening Islamic banking windows. Against this backdrop, this study aims to investigate the perceived gaps between managers and clients in Islamic marketing and banking, focusing on conventional banks’ Islamic banking windows. Design/methodology/approach Guided by a qualitative approach, semi-structured personal interviews and observations served as the data collection methods, involving 25 banks and 50 respondents in 3 different districts, namely, Shirajganj, Rajshahi and Chapainawabganj of Bangladesh from January to October 2023. The data were analysed using ATLAS.ti 2023 to explore codes and quotations derived from 14 interview questions. Further, ATLAS.ti 2023 facilitated synthesizing content, concepts, code occurrence, network analysis and thematic analysis. Findings Islamic and non-Islamic banks use Quranic verses, hadiths (prophetic traditions), images of mosques, the Kaaba and Arabic texts as Islamic marketing tools. These spiritual, divine and prescriptive tools are associated with Islamic banking. However, conventional banks receive criticism for having separate Islamic banking windows to serve religiously conscious clients, which generates tension among clients and bank managers. Practical implications The findings can theoretically assist academics in examining conventional banks’ Islamic marketing and banking practices, opening Islamic banking windows. Importantly, Shariah boards can play policy roles in safeguarding the function of Islamic marketing and banking. Managers can use the findings to anticipate client perceptions and enhance Islamic marketing and banking strategies. Likewise, the social implications include the explicit stance of Shariah to mitigate the mixture of halal and haram banking. Originality/value This pioneering study explores the perspectives of Islamic banking windows by non-Islamic banks. The combination of Islamic marketing and banking is a noteworthy novelty in this study and deserves recognition for its unique contribution to halal marketing and finance.