Exfoliated graphitic carbon nitride nanosheets (g-C3N4-NS) were applied for the first time for the preparation of an electrocatalyst for the oxygen reduction reaction (ORR). A less dense structure with increased surface area was observed for g-C3N4-NS compared to bulk g-C3N4 from detailed analyses including TEM, STEM, AFM with depth profiling, XRD, and UV-Vis spectroscopy. The pyrolysis of the prepared g-C3N4-NS with Co and carbon under an inert environment provided an enhanced accessibility to the N functionalities required for efficient interaction of Co and C with N for the formation of Co-N-C networks and produced a hollow and interconnected Co-N-C-NS structure responsible for high durability. The Co-N-C-NS electrocatalyst exhibited superior catalytic activity and durability and further displayed fast and selective four electron transfer kinetics for the ORR, as evidenced by various electrochemical experiments. The hollow, interconnected structure of Co-N-C-NS with increased pyridinic and graphitic N species has been proposed to play a key role in facilitating the desired ORR reaction.