Plasma processes have recently been utilized in many chemical reactions. Plasmas are good sources for generating active species, including electrons, ions, and radicals. A dielectric barrier discharge has been used to investigate the conversion of methane gas to higher hydrocarbons in AC non-equilibrium plasmas. The dielectric barrier discharge (DBD) provides a sufficiently high breakdown potential and thus electrons can reach to higher energies. Experiments were carried out at an atmospheric pressure and ambient temperatures. Non-equilibrium plasma was generated in a dielectric barrier discharge reactor by applying high voltages to the reactor electrodes. Activation of methane molecules led to the production of C₂ hydrocarbons and methanol. The effect of applied voltage, residence times, and feed mixtures such as helium and oxygen on methane conversion and product selectivity was studied. Our results show that conversion increases with increasing voltage and residence time while product selectivity is independent of the applied voltage. As the external voltage increases, the internal electric field across the region between the anode and the cathode goes up. Therefore, the number of energetic electrons within the discharge gap gets larger. As the number density of high-energy electrons increases, more collisions between methane molecules and those electrons take place. Thus the probability of breaking the bond between the carbon and hydrogen in the methane molecule becomes higher and the degree of dissociation and conversion increases. Helium appears to have no effect on conversion and selectivity at our applied voltages. Methane conversion increases significantly by introduction of oxygen in the feed stream. Inclusion of oxygen leads to the formation of methanol.