Variation of electrical resistivity of electroless nickel-coated carbon fibers heat-treated at different temperatures was investigated. The electrical resistivity was measured using the single fiber technique. Measurement results showed that as the heat treatment temperature increased, the resistivity decreased to a temperature of approximately 300 degreesC. A further increase of heat treatment temperature up to 450 degreesC, however, resulted in an increase of resistivity. Structural study using X-ray diffraction indicated that a large proportion of Ni3P is formed only above 300 degreesC, which is responsible for the increase of resistivity. Also, the increase of resistivity was found to be more pronounced and occurs at lower temperatures for samples with higher phosphorous content.