To achieve quantitative conformational characterization of oligosaccharides possessing branched structures with internal mobility, we developed a paramagnetic tagging protocol for NMR relaxation analysis. A nitroxide spin label was attached chemically to the reducing terminus of a specific high-mannose-type undecasaccharide that was overexpressed in genetically engineered yeast cells. This hybrid approach provides a source of long-distance atomic information, enabling detailed characterization of the conformational dynamics of the triantennary sugar chain that is involved in protein-fate-determination processes in cells.