Although the background of the banking system goes back as far as 1933, Islamic finance is still new in Afghanistan. The history of the first full-fledged Islamic bank began as recently as 2018 with the conversion of Bakhtar Bank, a conventional bank, to the Islamic Bank of Afghanistan (IBA). There have been numerous studies done worldwide, but no empirical study has examined the subject of Islamic banking adoption in the specific context of Afghanistan. Therefore, this present study investigates the adoption of Islamic banking in Afghanistan, using a case study of Herat province, based on Rogers’ (1983) Diffusion of Innovation Theory, to determine the impact of awareness, product knowledge, religiosity, relative advantage, compatibility, and complexity on the adoption of Islamic banking. A quantitative approach to the stratified convenience sampling method was used in this study. Questionnaires were distributed to 334 bank customers and the responses analyzed using SPSS v22. The multiple regression analysis finding indicated that product knowledge, relative advantage, and religiosity significantly and positively influenced the adoption of Islamic banking. It is suggested that the government and financial institutions should support Islamic banking with beneficial policies and initiatives to enhance the knowledge of the public about the significance of Islamic banking activities.