This paper investigates the effect of silane coupling agent on the magnetic properties of iron-phenolic soft magnetic composite materials at operating frequencies between 50 Hz and 1000 kHz. Coupling agents, cause a better wetting and a uniform coating distribution between the iron powders and the phenolic coating. The magnetic properties of the samples were measured by an LCR meter. The phase identification of coated powders was studied by XRD and the reaction of 3-aminopropyltriethoxy silane (APTS) with passived iron powders was characterized by FTIR. The results showed that the ring structure of aminosilane is broken up at pH similar to 8 and the amino groups become available for reaction with phenolic resin. It was shown that the compacted samples consist of passive/APTS/resin layers had lower loss factor and imaginary part of permeability in comparison with other samples. The difference in real part of permeability was negligible for APTS modified samples below 100 kHz. (C) 2009 Elsevier B.V. All rights reserved.