We present a detailed discussion of the three-interface surface plasmon resonance (SPR) geometry with the "angular interrogation" approach, and study the effect of thermal changes on the SPR curve through numerical simulations. An optical temperature sensor based on SPR, which has been shown to be a promising method to be used in the development of chemical, physical, and biomedical sensors, is proposed. The temperature sensor employs a three-interface SPR geometry where the layer making the interface with the environment has a refractive index highly sensitive to the changes in, the temperature of the environment. The resolution of the temperature measurement is dependent on the angular resolution of the detection system and the temperature sensitivity of the sensing layer. The comparison of thermal sensitivities of three and two-interface SPR geometries is also presented.