Secretory immunoglobulins (sIg), primarily IgA, control the microflora of the mucous membrane, protecting it from pathogens, as well as promoting its colonization by commensals. Knowledge of the specificity of sIgA (as well as sIgG) is necessary to understand their functions. We present here a protocol for using printed glycan array to profile the glycan specificity of sIg in oral fluid, with particular attention to sample preparation of this difficult-to-analyze material. The list of glycans in the array includes oligosaccharides typical of mucin O-chains, as well as bacterial polysaccharides, which are another full-fledged “player” in the sIg–mucin–microbiota system.