In sensory systems, peripheral organs convey sensory inputs to relay networks where information is shaped by local microcircuits before being transmitted to cortical areas. In the olfactory system, odorants evoke specific patterns of sensory neurons activity which are transmitted to output neurons in olfactory bulb glomeruli. How sensory information is transferred and shaped at this level remains still unclear. Here, using mouse genetics, 2-photon microscopy, electrophysiology and optogenetics, we identified a novel population of glutamatergic neurons (VGLUT3+) in the glomerular layer as well as several of their synaptic targets in the adult mouse olfactory bulb. Both peripheral and serotoninergic inputs controlled VGLUT3+ neurons firing. Furthermore, we show that VGLUT3+ neurons photostimulation in vivo strongly suppresses both spontaneous and odor–evoked firing of bulbar output neurons. In conclusion, we characterized a novel microcircuit controlling the transfer of sensory information at an early stage of the olfactory pathway.