We propose and experimentally demonstrate an on-chip all-optical multicasting (AOM) for 40 Gbit/s mode-division-multiplexed quadrature phase-shift keying (MDM-QPSK) signals based on a parallel dispersion-engineered multimode nonlinear silicon waveguide. Five dual-mode multicast wavelengths are successfully obtained on the generate idlers, and the power penalties of all the multicast channels are less than 1.1 dB at the bit error rate (BER) of 3.8×10-3. The dual-mode AOM scheme has the potential to promote the ability of optical cross-connect in practical hybrid multiplexed networks including MDM channels.