Purpose FinTech offers numerous prospects for significant enhancements and fundamental changes in financial services. However, along with the myriad of benefits, it also has the potential to induce risks to individuals, organisations and society. This study focuses on understanding FinTech developers’ perspective of the dark side of FinTech.Design/methodology/approach This study conducted semi-structured interviews with 23 Nigerian FinTech developers using an exploratory, inductive methodology The data were transcribed and then thematically analysed using NVivo.Findings Three themes – customer vulnerability, technical inability and regulatory irresponsibility – arose from the thematic analysis. The poor existing technological infrastructure, data management challenges, limited access to data and smartphone adoption pose challenges to a speedy integration of FinTech in the country, making customers vulnerable. The lack of privacy control leads to ethical issues. The lack of skilled developers and the brain drain of good developers present additional obstacles to the development of FinTech in Nigeria.Research limitations/implications FinTech operation in a developing country differs from that in developed countries with better technological infrastructure and institutional acceptance. This study recognises that basic banking operations through FinTech are still not well adopted, necessitating the need to be more open-minded about the global practicalities of FinTech.Practical implications FinTech managers, banks and policymakers can ethically collect consumer data that can help influence customer credit decisions, product development and recommendations using the mobile app and transaction history. There should be strict penalties on FinTech for selling customers’ data, sending unsolicited messages or gaining unnecessary access to the customer’s contact list. FinTech can offer to educate consumers about their financial management skills.Originality/valueWhereas other studies have focused on the positive aspects of FinTech to understand client perceptions, this study offers new insights into the dark side of FinTech by analysing the viewpoints of FinTech developers. Furthermore, the study is based in Nigeria, an emerging economy adopting FinTech, adding a new dimension to the body of knowledge.