The concurrent existence of three kinds of nano-scaled precipitates, ordered face-centered cubic β-Ni 3 Si, orthorhombic δ-Ni 2 Si and ordered face-centered cubic (Ni, Cr, Si)-rich phase, was found in a Cu–Ni–Si–Cr alloy during aging at 500°C by high resolution transmission electron microscopy and scanning transmission electron microscopy. It is the first time to report the precipitation of ordered fcc (Ni, Cr, Si)-rich phase in Cu–Ni–Si system alloys during aging. The morphology of β-Ni 3 Si precipitates changed from spheroid to ellipsoid with prolonged aging time. The δ-Ni 2 Si precipitates had its six variants lying on the {011} Cu habit planes and maintained disc-like during the whole aging process. The orientation relationships with copper matrix were as follows: (001) Cu //(001) δ , [110] Cu //[010] δ for δ-Ni 2 Si, and cube-on-cube ones for β-Ni 3 Si and (Ni, Cr, Si)-rich phase. The precipitation of (Ni, Cr, Si)-rich phase is responsible for high strength at overaging conditions as 500°C.