The present disclosure relates to a centering device for a nacelle of a turbojet engine providing the flush centering of an outer downstream panel of a thrust reverser with respect to a cowl of a fan casing. The centering device includes, in one single piece: a sub plate allowing the fixing of the centering device to the fan casing; a first positioning arm integrally formed with the sub plate, protruding upstream, in such a manner as to form, with respect to a directing axis (A) of the nacelle; a first radial abutment designed for guiding the cowl of the fan casing; and a second positioning arm, integrally formed with the sub plate, protruding downstream, in such a manner as to form, with respect to the directing axis (A) of the nacelle, a second radial abutment designed for guiding the outer downstream panel.