The effect of Nd and Co substitution on magnetic entropy changes and hysteresis losses has been investigated for the cubic NaZn13-type LaFe13−x Sixcompounds. Partially replacing La with Nd leads to a decrease of the Curie temperatureTC and an increase of the magnetic entropy change ΔS. Substitution of Co for Fe in La0.7Nd0.3Fe10.5Si1.5 can adjust TC to around room temperature. A large ΔS of 15J∕KgK at TC=280K for a field change from 0to5T and a small hysteresis loss close to zero near TC have been obtained in La0.7Nd0.3Fe10.7Co0.8Si1.5. The Co-doped NaZn13-type LaNdFeSi compounds may be a suitable candidate for magnetic refrigerant near room temperature.