The dentate gyrus is the entrance of the hippocampal formation and a primary target of excitatory afferents from the entorhinal cortex that carry spatial and sensory information. Mounting evidence suggests that continual adult neurogenesis contributes to appropriate processing of cortical information. The ongoing integration of adult born neurons dynamically modulates connectivity of the network, potentially contributing to dentate cognitive function. Here we review the current understanding of how glutamatergic innervation develops during the progression of adult-born neuron maturation. Summarizing the developmental stages of dentate neurogenesis, we also demonstrate that new neurons at an immature stage of maturation begin to process afferent activity from both medial and lateral entorhinal cortices.