Despite the extensive research that has been carried out on organic nanoparticles, little explanation has been provided for the reasons behind their exceptional properties. In this work, the effect of the particles being on the nanoscale on the thermal decomposition kinetics of organic particles was examined by means of a dynamic vacuum stability test. Nano- and microscale particles of 1,3,5-triamino-2,4,6-trinitrobenzene were measured for comparison. Analysis of the evolved gas revealed that the nanoparticles (NPs) show much higher reaction activity than the microparticles (MPs). Both the non-isothermal and isothermal reaction mechanisms and kinetics were computed. The NPs and MPs exhibit different reaction mechanisms, while similarly sized particles follow different mechanisms for different stages of the reaction. The mechanisms for the NPs are affected by the temperature in the range considered. NPs have larger values for the apparent activation energy (E(a)) and pre-exponential factor (A) than MPs and the relationship of E(a) to A demonstrates that a kinetic compensation effect is evident. The nanoscale effect shows there to be a significant influence on the apparent performances and kinetics as well as on the intrinsic reaction mechanisms of organic particles. This effect can be attributed to the surface properties of NPs, where the high surface area contributes to efficient mass transfer and heat transfer, thus leading to numerous activated molecules being involved in the reaction.