Biodegradable piezoelectric polymers have emerged as a hot research focus in bioelectronics, energy-harvesting systems, and biomedical applications, as well as in sustainable future development. Biopolymers possess plenty of features which make them promising candidates for next-generation electronic technologies, including biocompatibility, degradability, and flexibility. This review discusses piezoelectric biopolymers, focusing on the relationship between coupling mechanisms, material structures, and piezoelectric performance. Processing techniques such as annealing, mechanical drawing, and poling are introduced and further studied in terms of achieving high piezoelectric performance. This work reviews the strategies for enhancing piezoelectric properties via molecular engineering, nano structuring, and the incorporation of additives. Furthermore, the applications of these biopolymers in energy harvesting and biomedicine are provided, with a discussion of their potential in degradable bioelectronic devices. There are still challenges in optimizing piezoelectric performance and ensuring stability. Our research is expected to provide an understanding of these challenges and help to achieve a wider application of piezoelectric biopolymers.