Nano-sized Fe and Co particles were synthesized by chemical vapor condensation (CVC) using the precursors of iron carbonyl (Fe(CO)(5)) and cobalt carbonyl (Co-2(CO)(8)) as the sources. Microstructures and magnetic properties were investigated by means of Mossbauer spectroscopy, XPS, HRTEM and BET. The synthesized particle has nearly spherical shape consisting of core-shell type structures with mean particle size of 5-20nm. The magnetic states of iron nanoparticles changed from superparamagnetism to ferromagnetism depending on the particle size and microstructure. Oxygen content in the carrier gas influenced markedly both the microstructure and magnetic properties of iron and cobalt nanoparticles.