Temperature dependences of the electrical resistivity have been measured on the Heusler alloy system Ni2MnGa1−xFex. The phase diagram of Ni2MnGa1−xFex was constructed on the basis of the experimental results. The structural and magnetic transition temperatures are consistent with those previously determined by magnetic measurements. The changes of the electrical resistivity at the martensitic transition temperature, ∆ρ, were studied as a function of Fe concentration x. The ∆ρ abruptly increased in the concentration range between x = 0.15 and 0.20. The magnetostructural transitions were observed at x = 0.275, 0.30, and 0.35.