AbstractPoly‐N‐acetyllactosamine (PLN) is a unique glycan composed of repeating units of the common disaccharide (Galβ1,4‐GlcNAcβ1,3)n. The expression of PLN on glycoprotein core structures minimally requires enzyme activities for β1,4‐galactosyltransferase (β4GalT) and β1,3‐N‐acetylglucosminyltransferase (β3GnT). Because β4GalTs are ubiquitous in most cells, PLN expression is generally ascribed to the tissue‐specific transcription of eight known β3GnT genes in mice. In the olfactory epithelium (OE), β3GnT2 regulates expression of extended PLN chains that are essential for axon guidance and neuronal survival. N‐glycan branching and core composition, however, can also modulate the extent of PLN modification. Here, we show for the first time that the β1,6‐branching glycosyltransferase GCNT2 (formerly known as IGnT) is expressed at high levels specifically in the OE and other sensory ganglia. Postnatally, GCNT2 is maintained in mature olfactory neurons that co‐express β3GnT2 and PLN. This highly specific co‐expression suggests that GCNT2 and β3GnT2 function cooperatively in PLN synthesis. In support of this, β3GnT2 and GCNT2 co‐transfection in HEK293T cells results in high levels of PLN expression on the cell surface and on adenylyl cyclase 3, a major carrier of PLN glycans in the OE. These data clearly suggest that GCNT2 functions in vivo together with β3GnT2 to determine PLN levels in olfactory neurons by regulating β1,6‐branches that promote PLN extension. J. Cell. Physiol. 229: 471–478, 2014. © 2013 Wiley Periodicals, Inc.