We demonstrate magneto-optical effects in silver nanoparticles with magnetic circular dichroism (MCD) spectroscopy. The MCD spectra show a derivative-like (splitting) signal in the localized surface plasmon absorption region. The observed magneto-optical (magnetoplasmonic) response can be due to the increase in the Lorentz force imparted on the collective electrons that move in left and right circular orbits in the nanoparticles. Importantly, simultaneous deconvolution analysis of UV-vis absorption and MCD spectra provides an accurate shift frequency (or cyclotron frequency) as well as bandwidths of these two magnetoplasmonic modes consistently. A very large cyclotron frequency is found in the surface magnetoplasmons under a magnetic field of 1.6 T, suggesting an apparent enhancement of the local magnetic induction in the nanoparticles. (C) 2014 Published by Elsevier B.V.