Abstract Fucosylated chondroitin sulfate (FCS) is a unique polysaccharide, first described nearly four decades ago, and found exclusively in sea cucumbers. It is a component of the extracellular matrix, possibly associated with peculiar properties of the invertebrate tissue. The carbohydrate features a chondroitin sulfate core with branches of sulfated α-Fuc linked to position 3 of the β-GlcA. FCSs from different species of sea cucumbers share a similar chondroitin sulfate core but the structure of the sulfated α-Fuc branches varies significantly. The predominant pattern consists of a single unit of sulfated α-Fuc, though some species exhibit branches with multiple α-Fuc units. This comprehensive review focuses on four major aspects of FCS. Firstly, we describe the initial approaches to elucidate the structure of FCS using classical methods of carbohydrate chemistry. Secondly, we highlight the impact of two-dimensional NMR methods in consolidating and revealing further details about the structure of FCS. These studies were conducted by various researchers across different countries and involving multiple species of sea cucumbers. Thirdly, we summarize the biological activities reported for FCS. Our survey identified 104 publications involving FCS from 42 species of sea cucumbers, reporting 10 types of biological activities. Most studies focused on anticoagulant and antithrombotic activities. Finally, we discuss future perspectives for studies related to FCS. These studies aim to clarify the evolutionary advantage for sea cucumbers in developing such a peculiar fucosylated glycosaminoglycan. Additionally, there is a need to identify the enzymes and genes involved in the metabolism of this unique carbohydrate.