Graphene films and ribbons were grown on Ni-coated Si substrates using the microwave plasma enhanced chemical vapor deposition method. We report the structure, morphology, and quality of graphene films and ribbons. The semiconducting nature of the CVD-grown graphene was observed by studying resistance−temperature variation in the range 25 to 200 °C, using the four-point probe method. Graphene exhibited an increase of resistance upon exposure of CO and a decrease in resistance upon pure O2 and NO2 exposures. It was observed that graphene films show sensor signal ∼3 and 35 for 100 ppm of CO and 100 ppm of NO2 whereas the graphene ribbons show the sensor signal values of 1.5 and 18 for 100 ppm of CO and 100 ppm of NO2. The gas sensor mechanism was observed to be mainly dependent on the charge carrier transfer on conducting graphene surfaces caused by the adsorption of gases.