Fe microflakes with uniform size and well-defined shape were successfully synthesized by hydrogen-thermal reduction of α-Fe₂O₃ precursor microflakes. The hexagonal Fe microflakes have edge lengths of about 5 μm and thicknesses of about 500–1000 nm. The complex permittivity and permeability of Fe microflakes–paraffin composite were measured using a vector network analyzer in the 2–18 GHz frequency range. Remarkable dielectric relaxation, natural resonance and exchange resonance were observed in the complex permittivity and permeability spectrum. Electromagnetic wave absorption (EMA) performance of samples was evaluated by using transmission line theory. An excellent microwave absorption performance was obtained for a coating containing Fe microflakes as filler, in which the maximum reflection loss is −15.3 dB and effective EMA band (RL < −10 dB) covers the whole frequency range of 12.2–16.6 GHz.