Both　Fe　nanoparticles　(Fe　NPs)　and　bimetallic　Fe/Ni　nanoparticles　(Fe/Ni　NPs)　were　synthesized　using　eucalyptus　leaf　extracts.　More　than　eight　major　compounds　in　eucalyptus　leaf　extracts,　which　may　serve　as　reducing　and　capping　agents,　were　identified　using　Gas　Chromatography-Mass　Spectrometer　(GC-MS).　The　obtained　Fe　NPs　and　Fe/Ni　NPs　were　characterized　using　Fourier　Translation　Infrared　Spectroscopy　(FTIR),　Thermogravimetric　Analysis　(TG),　Scanning　Electron　Microscopy　(SEM),　Energy　Dispersive　X-ray　Spectroscopy　(EDS),　X-ray　Diffraction　(XRD),　and　X-ray　Photoelectron　Spectroscopy　(XPS).　The　results　demonstrated　that:　(1)　the　presence　of　Fe　in　Fe　NPs,　and　Fe　and　Ni　in　Fe/Ni　NPs;　(2)　the　coating　organic　compounds　may　be　responsible　for　the　capping　and　efficient　stabilization　of　Fe　and　Fe/Ni　NPs.　Fe　NPs　and　Fe/Ni　NPs　were　then　used　to　degrade　methyl　orange　(MO)　in　aqueous　solution.　Only　29.2%　of　MO　was　removed　from　aqueous　solution　using　Fe　NPs,　while　99.6%　of　MO　was　removed　using　Fe/Ni　NPs.　Furthermore　the　removal　of　MO　using　Fe　NPs　and　Fe/Ni　NPs　followed　pseudo-first-order　kinetics.　(C)　2016　Elsevier　B.V.　All　rights　reserved.