The influence of doping with the 5d transition metal W has been studied in the quaternary (Mn,Fe)2(P,Si) based giant magnetocaloric compounds, which is one of the most promising systems for magnetic refrigeration. It is found that W substitution can separately decrease the Curie temperature TC and retain the thermal hysteresis ∆Thys at an almost constant level (∼5 K) for Mn0.6Fe1.27-xWxP0.64Si0.36 (x ≤ 0.02). Low-content W doping conserves the good magnetocaloric effect (MCE) without an obvious degradation. For x ≤ 0.02 the average magnetic entropy change |∆Sm| amounts to 11.4 Jkg−1K−1 for an applied magnetic field change of 2 T and the adiabatic temperature change ∆Tad amounts to 3.9 K for an applied magnetic field change of 1.5 T. The occupancy of substitutional W atoms is determined by XRD experiments and DFT calculations. Our studies provide a good strategy to further optimize the MCE of this material family.@en