The doping effect of N in hydrogenated amorphous silicon (a‐Si:H) is studied. The absence of a thickness dependence of the conductivity of N‐doped samples provides convincing evidence that the doping effect of N ina‐Si:H is a bulk property. The similarity between the effect of N doping and that of P doping found in the conductivity and the photoconductivity decay indicates that N can act as an effective donor ina‐Si:H and that N doping is also of substitutional type; however, the solid‐phase doping efficiency of N is estimated to be at least three orders of magnitude lower than that of P.