The development of electronic products and increased electronic waste have triggered a series of ecological problems on Earth. Meanwhile, amidst energy crises and the pursuit of carbon neutrality, the recycling of discarded biomass has attracted the attention of many researchers. In recent years, the transformation of discarded biomass into value-added electronic products has emerged as a promising endeavor in the field of green and flexible electronics. In this review, the attempts and advancements in biomass conversion into flexible electronic materials and devices are systematically summarized. We focus on reviewing the research progress in biomass conversion into substrates, electrodes, and materials tailored for optical and thermal management. Furthermore, we explore component combinations suitable for applications in environmental monitoring and health management. Finally, we discuss the challenges in techniques and cost-effectiveness currently faced by biomass conversion into flexible electronic devices and propose improvement strategies. Drawing insights from both fundamental research and industrial applications, we offer prospects for future developments in this burgeoning field.