Urea is one of the main nitrogen fertilizers used in agriculture. But being well soluble in water, hardly 50% of its nitrogen is assimilated by plants. One possibility to eliminate this disadvantage is to use coating agents for modification of urea to obtain a controlled-realized fertilizer. The aim of this research was to study the influence of different lime-containing additives on the thermal behavior and decomposition kinetics of urea in oxidizing atmosphere. Commercial fertilizer-grade urea (46.4% N) and analytical-grade CaO, MgO, CaCO3, MgCO3 were used in the experiments. In addition, one Estonian limestone and one dolomite sample were used as additive or coating material. The experiments with a Setaram Setsys 1750 thermoanalyzer coupled to a Nicolet 380 FTIR Spectrometer by a heated transfer line were carried out under non-isothermal conditions up to 900 degC at the heating rate of 5 degC min-1 and to calculate kinetic parameters, additionally, at 1, 2, and 10 degC min-1 in the atmosphere containing 80% of Ar and 20% of O2. The differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results obtained indicate that thermo-oxidative decomposition of urea as well as the blends of urea with lime-containing materials and urea prills coated with limestone or dolomite powder follows a complex reaction mechanism.