Labeling of released asparagine-linked (N-linked) oligosaccharides from glycoproteins is commonly performed to aid in the separation and detection of the oligosaccharide. Of the many available oligosaccharide labels, 2-amino benzamide (2-AB) is a popular choice for providing a fluorescent product. The derivatization conditions can potentially lead to oligosaccharide desialylation. This work evaluates the extent of sialic acid loss during 2-AB labeling of N-linked oligosaccharides released from bovine fetuin, polyclonal human serum IgG, and human α1-acid glycoprotein as well as of sialylated oligosaccharide reference standards and finds that for more highly sialylated oligosaccharides the loss is greater than the <2% value commonly cited. Manufacturers of glycoprotein biotherapeutics need to produce products with a consistent state of sialylation, and therefore require an accurate assessment of glycoprotein sialylation.