During exploration, animals form a cognitive map of an environment by combining specific sensory cues or landmarks with specific spatial locations, a process which critically depends on the mammalian hippocampus. The dentate gyrus (DG) is the first stage of the canonical hippocampal trisynaptic circuit and plays a critical role in contextual discrimination, yet it remains unknown how neurons within the DG encode both spatial and sensory information during cognitive map formation. Using two photon calcium imaging in head fixed mice navigating a virtual linear track, along with on-line sensory cue manipulation, we have identified robust sensory cue responses in DG granule cells. Granule cell cue responses are stable for long periods of time, selective for the modality of the stimulus and accompanied by strong inhibition of the firing of other active neurons. At the same time, there is a smaller fraction of neurons whose firing is spatially tuned but insensitive to the presentation of nearby cues. These results demonstrate the existence of "cue cells" in addition to the better characterized "place cells" in the DG. We hypothesize that the observed diversity of representations within the granule cell population may support parallel processing of complementary sensory and spatial information.