Glycosaminoglycan (GAG) is a family of linear, sulfated polysaccharides ubiquitous to all mammals. GAG plays important roles in many biological processes, including cell differentiation, growth, and mobility. Much of GAG’s activity is intimately linked to its interaction with proteins. As a powerful structural biology tool, solution NMR has played a crucial role in investigating protein-GAG interactions. One especially useful tool in solution NMR studies of protein-GAG interactions is the use of paramagnetically-labeled GAG oligosaccharides. Paramagnetism provides a sensitive and information-rich method to identify both the binding site as well as the binding orientations of GAG. In this chapter, we will detail the procedure for the purification of heparin oligosaccharides and their paramagnetic functionalization, as well as the subsequent nuclear magnetic resonance (NMR) experiments needed to quantify the paramagnetic effect of the GAG oligosaccharide on the target protein.