Non-invasive gamma entrainment using light stimulation at 40 Hz can reduce levels of amyloid beta peptide and improve memory performance in several mouse models of Alzheimer’s disease. While light flickering was shown to increase the gamma frequency component of hippocampal oscillations, the mechanisms that transduce visual stimulation into cellular and circuit changes remain elusive. Because neurogenesis in the aging hippocampus is particularly sensitive to electrical activity, the effects of gamma entrainment might be revealed by analyzing its impact on developing new neurons. Using light flickering, we studied the impact of 40 Hz stimulation on the development of neurons born in the dentate gyrus of 8-month-old mice. Gamma entrainment boosted adult neurogenesis, as shown by a significant increase in doublecortin labeling, a marker for immature neurons. We also found that dendrites grow faster in developing granule cells from entrained mice, suggesting enhanced levels of connectivity. These preliminary results reveal that light flickering at 40 Hz awakes mechanisms that promote neuronal plasticity not only under pathological conditions, but also in the healthy aging brain.