NG2 cells comprise a heterogeneous precursor population but molecular markers distinguishing between the assumed NG2 cell subpopulations are lacking. Previously, we described that a subfraction of the synaptic cell adhesion molecule SynCAM 1 is modified with the glycan polysialic acid (polySia) in NG2 cells. As for its major carrier, the neural cell adhesion molecule NCAM, polySia attenuates SynCAM 1 adhesion. Functions, as well as cellular and subcellular distribution of polySia‐SynCAM 1 are elusive. Using murine glial cultures we now demonstrate that polySia‐SynCAM 1 is confined to the Golgi compartment of a subset of NG2 cells and transiently recruited to the cell surface in response to depolarization. NG2 cells with Golgi‐confined polySia were NCAM‐negative, but positive for markers of oligodendrocyte precursor cells (OPCs). Consistent with previous data on polySia‐SynCAM 1, polySia in Ncam−/− NG2 cells was exclusively attached to N‐glycans and synthesized by ST8SIA2, one out of two mammalian polysialyltransferases. Unexpectedly, Golgi‐confined polySia was also detected in Ncam−/− microglia, but this fraction resided on O‐glycans and was produced by the second polysialyltransferase, ST8SIA4, indicating the presence of yet another polySia carrier in microglia. Searching for this carrier, we identified polysialylated neuropilin‐2, so far only known from dendritic cells and exudate macrophages. Microglia activation by LPS, but not interleukin‐4, caused a transient translocation of Golgi‐localized polySia to the cell surface, resulting in complete depletion. Finally, NO‐production of LPS‐stimulated microglia was attenuated by addition of polySia suggesting that the observed loss of polySia‐neuropilin‐2 is involved in negative feedback regulation of pro‐inflammatory microglia polarization. GLIA 2015;63:1240–1255