A novel iron-coated carbon fiber was fabricated electrochemically. The magnetic properties, complex permeability, and complex permittivity were measured. It was found that iron-coated fiber-epoxy composites with different mass loadings have different magnetic resonance frequencies. The resonance frequency of the 75 wt% sample is higher than that of the 80 wt% sample due to the influence of the demagnetization field. The ε e ' value of both composite samples exhibits a high value in the frequency range of 2 to 18 GHz, which is due to the longer conducting length of the fiber and the good conductivity of the iron. The values of ε e '' are also high, which is attributed to the intrinsic electric property of the carbon fiber.