This paper summarizes our group’s work on a novel thiolation method and discusses the potential applications of highly thiolated oligo- and polysaccharides. Thiolation of oligo- and polysaccharides was performed using phosphorus pentasulfide, resulting in a high degree of modification. Among the products, β-cyclodextrin (β-CD) was per-thiolated, leading to an 89-fold increase in mucoadhesion compared to the native oligosaccharide and a significantly prolonged residence time. This beneficial property was demonstrated not only in vitro but also in animal studies, where the per-thiolated CD remained in large amounts in the GI tract after 8 hours, while native β-CD was already completely eliminated. Reactive disulfide-protected thiolated CDs were synthesized with various protecting groups; in all cases, more pronounced mucodiffusion was observed for the S-protected thiomers compared to non-protected ones, along with increased mucoadhesion and cellular uptake. These results confirm that the highly thiolated oligo and polysaccharides have strong potential as oral or parenteral drug delivery vehicles.