The ability of antibodies to extravasate out of blood vessels is critical for therapeutic activity, because molecular targets for most diseases are located outside of the endothelial lining. By performing detailed biodistribution studies with a novel IL9-armed cancer-specific antibody, we identified a clear correlation between N-linked glycan structures and tumor-targeting efficiencies. Site-specific glycan analysis provided a detailed view of the glycan microheterogeneity present on the IL9 portion of the recombinant protein. Nonsialylated glycan structures have a negative impact on disease-homing activity, highlighting the importance of glycosylation control and characterization during process development.