Financial technology (FinTech) presents a transformative opportunity for Islamic banks in Nigeria to enhance financial inclusion. However, its potential remains unrealized due to significant demand-side barriers, including a lack of understanding of Islamic banking and low adoption rates. While existing research has focused on supply-side and macroeconomic factors, a critical gap exists in understanding the behavioural determinants influencing FinTech acceptance within this specific context. This study, therefore, investigates the impact of behavioural factors on the acceptance of FinTech among users of Islamic banking in Nigeria. A quantitative research design was employed, utilizing a structured questionnaire distributed to a sample of 384 staff and customers of Jaiz and Taj Banks. Data were analyzed using Structural Equation Modeling (SEM). The findings reveal that customer innovativeness and perceived ease of use are the most significant positive predictors of acceptance. Subjective norms also had a significant, though weaker, positive influence. Contrary to conventional technology adoption theories, perceived usefulness and trust were found to have no significant impact, while self-efficacy showed a negative relationship. The study concludes that acceptance is driven more by personal innovativeness and user-friendly design than by perceived utility or trust. These insights provide crucial guidance for Islamic banks and policymakers to design targeted, culturally-sensitive strategies that prioritize ease of use, leverage social influence, and cater to innovative customer segments to accelerate FinTech adoption and foster greater financial inclusion.