Hippocampal dentate gyrus (DG) is essential for encoding highly similar inputs into distinct neural representations. This function is mainly attributed to the sparsely firing excitatory granule cells. It is not known how excitatory DG neurons modify their firing patterns in response to different conditions, to facilitate learning. We studied the activity of excitatory DG neurons during discrimination fear conditioning task (FC) using in vivo one-photon calcium imaging in adult, healthy C57/black mice. We compared learning in males (n = 6) and females (n = 6) and further, in voluntarily running females (n = 6). To this end, we injected AAV.CamKII.GCaMP6s.WPRE.SV40 to express GCaMP6s and implanted a lens targeting the dorsal dentate gyrus. We imaged DG neurons during a 20-day FC, in which the mice explored two highly similar contexts, one of which predicted the occurrence of foot-shock(s) from day 11 onwards. According to our results, males and sedentary females learnt to discriminate the contexts, whereas the runner females did not. Overall, males discriminated better than females, and females showed a stronger and more generalized fear response than males. Preliminary calcium signal analysis revealed that DG neurons had a low selectivity to the contexts. Potential modulation in the firing patterns was found in males: in the foot-shock context, the number of events across the active DG neurons before and after conditioning were less correlated compared to the safe context. In conclusion, DG neurons seem to link contextual memories in both sexes and respond to fear in males.