The stability of silver nanoparticles (Ag NPs) attracts an increasing attention because of the broadening field of their application, especially in catalysis, medicine and pharmacy, electronics and optoelectronics, sensors, environment protection technologies, textronics and many others. In this article, the stability of electrostatically stabilized aqueous dispersions of Ag NPs with different sizes under irradiation and thermal treatment is discussed. The UV–Vis spectrophotometry supported by Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) were used to monitor the changes induced in Ag NPs by temperature, laser and electron-beam irradiation. It was found that the nature and mechanism of size and shape changes in Ag NPs treated by elevated temperature and radiation are different. KBr added to the reacting mixture as a size-control agent determines also the stability of investigated Ag NPs. The higher KBr content, the lower Ag NPs size, but surprisingly the highest thermal and photostability. Both thermal and radiation treatments lead to narrower distribution of Ag NPs sizes. The effects induced by laser light strongly depend on the relationship between the maximum of the plasmonic absorption band and wavelength of laser light. Small doses of electron beam radiation (≤ 100 Gy) does not change the NPs immediately. However a strong post radiation effect was found. The lower applied dose, the stronger effect observed.