Abstract Boron/phosphorus substitution in Fe 2P has been studied by 57Fe Mössbauer spectroscopy. The magnetic ordering temperature increases rapidly with increasing boron content. Replacement of a phosphorus atom by boron in the immediate environment of an iron atom results in a substantial increase of the magnetic hyperfine field, while the centroid shift and the quadrupole splitting are almost unchanged. The hyperfine parameters for iron atoms at larger distances from the boron atom remain unaffected. Boron substitutes preferentially for phosphorus at the singlefold P(2) position in the Fe 2P structure.