Fe(H2PO4)(2)center dot 2H(2)O was synthesized by a simple and cost-effective method using iron metal and phosphoric acid as starting chemicals. The thermal transformation products from the synthesized Fe(H2PO4)(2)center dot 2H(2)O according to the thermal treatment at 423 and 673 K were found to be FeH2P2O7 and Fe2P4O12, respectively. The activation energies of decomposition reaction of Fe(H2PO4)(2)center dot 2H(2)O were calculated through the isoconversional methods of Ozawa and Kissinger-Akahira-Sunose. The synthesized Fe(H2PO4)(2)center dot 2H(2)O and its thermal transformation products were characterized by scanning electron microscopy, X-ray powder diffraction, and FTIR spectroscopy. Room-temperature magnetization results showed a ferromagnetic behavior of the Fe(H2PO4)(2)center dot 2H(2)O and its thermal transformation products. The hysteresis loops were in the range - 10000 Oe < H < + 10000 Oe. and the strong specific magnetization values were in the range 32.25-96.28 emu/g at 10 kOe.