The presently disclosed subject matter provides nitric oxide-releasing polysaccharides and oligosaccharides, in particular, polyglucosamines, and their use in biomedical and pharmaceutical applications. More particularly, in some embodiments, the presently disclosed subject matter provides nitric oxide-releasing polysaccharides and oligosaccharides that release nitric oxide in a controlled and targeted manner, thereby prolonging the therapeutic effects of nitric oxide and improving the specificity of nitric oxide delivery to targeted cells and/or tissues.