The magnetic and magneto-optical properties of NdX (X = P, As, Sb, Bi) in the ferromagnetic phase derived from an electronic structure calculation have been presented. The calculation is performed using the local spin-density approximation (LSDA) and also the LSDA corrected with the Coulomb interaction U (the LSDA+U). The LSDA+U density of states at the Fermi level is small and the carrier density is also low. The magnetism in NdP, NdAs and NdSb is found to be dominated by a large orbital contribution coupled antiparallel to the spin moment. The anisotropic mixing between the p states of X and the f states of Nd provides the large off-diagonal optical conductivity.