Broadband modulation of magnetic circular dichroism (MCD) using a relatively low magnetic field or by producing a field-free magnetoplasmonic effect in the remnant magnetic state was achieved by the integration of the noble metals (NMs) Au and Ag and the perpendicular magnetic anisotropy of Co with ZnO nanowires (NWs) used as the template. The samples containing NMs revealed MCD sign reversals and enhancements when compared with the original Co/ZnO NWs. The magnetoplasmonic effect of Au close to the visible light spectrum could induce the CD change in the visible region. Notably, the ultraviolet (UV) CD in Ag/Co/ZnO NWs is 12.5 times larger under a magnetic field (∼0.2 T) and 10 times greater in the remnant state (field-free) than those of the original Co/ZnO NWs because of the magnetoplasmonic effect of Ag in the UV spectrum. These results are attributable to the coupling of the remnant magnetic state of Co magnetization, the magnetoplasmons of the NMs, and the excitons of the ZnO NWs. The findings are potentially applicable in magneto-optical recording, biosensing, and energy contexts involving magnetoplasmonic functionalization.