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High-entropy alloys (HEAs) with a single-phased face-centered-cubic structure possess excellent plasticity but generally low strength. Precipitation strengthening is one of the most promising methods to improve the strength of alloys. However, plagued by a nerve-wracking fact that strength-ductility trade-off frequently limits the improvement of alloy properties. To overcome this problem, a new Ni₃₅(CoFe)₅₅V₅Nb₅ HEA with an excellent strength and ductility synergy was developed by introducing a novel bifunctional L1₂-Ni₃Nb nano-precipitate. This HEA exhibits a high yield strength of 855 MPa, ultimate tensile strength of 1,302 MPa and marvelous elongation of ∼ 50%. First-principles calculations show that the (Ni₂₄Co₁₈Fe₆)₃(Nb₁₀V₄Fe₂) nano-precipitate with a L1₂ structure possesses lower formation energy than that with D0₂₂ structure. The novel nano-precipitates provide two-fold functions. On the one …