Bio-based admixtures (BBAs) are emerging as a promising class of additives for concrete, offering a more sustainable and environmentally friendly alternative to conventional chemical admixtures. Derived from various natural or biological sources, including plants, animals, and microorganisms, BBAs have shown potential in enhancing the performance characteristics of concrete in several key areas. This review article provides an in-depth exploration of BBAs, beginning with a detailed classification of the different types of BBAs based on their source material and production methods. It then delves into the various characterization techniques used to assess the properties and performance of BBAs, providing insights into their impact on the workability, strength, durability, and rheology of concrete. The article also discusses the diverse application areas of BBAs, highlighting their versatility and potential for wide-ranging use in the construction industry. It further identifies and discusses the challenges associated with the use of BBAs, such as issues related to compatibility with different types of cement and concrete, storage and shelf-life considerations, quality control and standardization concerns, and cost-effectiveness. In conclusion, the review emphasizes that while BBAs hold great promise as an alternative to conventional chemical admixtures for concrete, there is a need for more interdisciplinary collaboration and research to overcome the identified challenges and fully realize their potential. The paper calls for further studies focusing on optimizing the production and application processes of BBAs, as well as developing standardized testing and quality control procedures.