Individual nitrates, UO2(NO3)2.6H2OandFe(NO3)3.9H2O as well as their binary mixtures in various mol ratios have been studied using simultaneous thermal techniques and X-ray powder diffraction measurements. Nature and stoichiometry of hydroxynitrates of iron and uraniumwere altered by changing the heating rates for the equal mass of binary nitrate mixtures under identical gas flow conditions. Evolved gas analysis and thermogravimetric measurements indicated the absence of direct interaction between two nitrates in the binary nitratemixtures. Both the nitrates decomposed independently in the mixtures to their respective oxides. These results have been supported by X-ray powder diffraction measurements. Phase diagram of UO2(NO3)2.6H2O–Fe(NO3)3.9H2O system containing 0–100 mol% of UO2(NO3)2.6H2O was constructed using differential thermal analysis technique. The formation of the eutectic at 33oC for 50 mol% uranyl nitrate hexahydrate–50 mol% iron (III) nitrate nonahydrate mixture has been observed for the first time.