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The influence of Cu doping on phase transition, thermal strain, and thermal expansion property of polycrystalline Ni50Mn23−xCuxGa27(x= 1, 3, 5, 6 and 7) alloys is investigated. The results show that with increasing Cu concentration, martensitic transformation gradually gets close to Curie transition. A magnetostructural transition (MST) is observed in samples with x= 6 and 7. Such MST can enhance magnitude of transformation strain. Besides, Ni50Mn23−xCuxGa27alloys possess an isotropic, recoverable, and thermally stable thermal strain. Excitedly, Cu doping can effectively tune the phase transition, thermal strain, and thermal expansion properties of Ni50Mn23−xCuxGa27alloys. Adjustable coefficients of thermal expansion from positive to negative are obtained by Cu‐doped Ni50Mn23−xCuxGa27alloys. The average linear expansion coefficient (α) between −140.44 and −207.70 ppm K−1is observed in samples with x= 6 and 7 for a narrow temperature span of 11–14 K. When the temperature span is about 72 K (x= 6) and 73 K (x= 7), which is the largest temperature span observed in Ni–Mn–Ga‐based alloys recently, the α values decrease to about −36 ppm K−1. These findings are beneficial for manipulating the thermal expansion property of Ni–Mn–Ga–Cu alloys and their multifunctional applications. Cu doping not only changes the sign of the thermal expansion coefficient from positive to negative but also broadens the temperature span of NTE (ΔTN) in Ni50Mn23−xCuxGa27alloys. Such a large temperature span of ΔTN= 72–74 K with α= −36 ppm K−1is first observed in Ni–Mn–Ga–Cu alloys.