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This paper unprecedentedly reports the effect of metal (nickel) coating on the stress-dependent electric permittivity, piezoelectricity and piezoresistivity of carbon fiber. Both permittivity (2 kHz) and DC conductivity of carbon fiber are increased by nickel coating. For 7-μm diameter carbon fiber, nickel coating (0.25-μm thickness) increases the relative permittivity from 12,200 to 63,200, and decreases the resistivity from 1.5 × 10⁻⁵ to 1.5 × 10⁻⁷ Ω.m. The relative permittivity of the nickel coating (Rule of Mixtures) is 404,600 - similar to 405,300 for nickel wire (160-μm diameter). The resistivity of the nickel coating (Rule of Mixtures) is 2.0 × 10⁻⁸ Ω.m - lower than 8.8 × 10⁻⁸ Ω.m for the nickel wire - probably because of the higher degree of preferred crystallographic orientation in the nickel coating. The nickel structure affects the conduction more than polarization. The piezoelectric and piezoresistive effects are …