In light of increasing global challenges like climate change, carbon neutrality, and biodiversity loss, the need for sustainable solutions is essential. Green FinTech innovation, which combines financial resources, services, and technologies, has become a significant area of focus for addressing these issues. However, despite growing interest from various stakeholders, progress towards sustainable development remains slow due to fragmented academic knowledge. This study aims to bridge this gap by offering practical guidelines for those involved in green FinTech innovation. By examining the new service development process, including both the front-end and back-end stages, the study will identify key influencers such as customers, organizations, and partners. Semi-structured interviews will be conducted with three green FinTech case studies in Thailand, specifically focusing on rental electric bike services, energy trading systems, and solar rooftop platforms. The research will investigate the concepts, methods, and critical success factors that drive the innovation processes of these projects through a comparative multi-case study. The findings will reveal different paths for B2B and B2C green FinTech innovation, emphasizing the importance of external factors. Successful innovation requires a thorough understanding of customer behavior, beyond just pro-environmental tendencies. These insights aim to accelerate green FinTech innovation in emerging economies and underscore the need for further quantitative research to validate these findings. This research will provide valuable insights for policymakers, financial institutions, and innovators, supporting the advancement of sustainable development through green FinTech solutions.