Silicone-based materials are of great interest in medicine and cosmetic applications because of their biocompatibility and elasticity. Recently, there has been a significant focus on the development of functional materials that integrate multiple desirable characteristics. Elastic composites reinforced with magnetic filler are active in a magnetic field. These materials can be an interesting alternative to the currently used materials, after appropriate modification of the NdFeB powder. From the point of view of the use of materials in biomedical engineering, they require a lot of research and analysis to determine whether they are useful and will not cause potentially negative effects on a living organism. The aim of the work was to verify the influence of the powder silanization method on the thermal and physicochemical properties of silicone-based composites reinforced with NdFeB powder. The appropriate selection of the silanization parameters used in the process allows control of the properties of the composite. The powder surface silanization execution affects the physicochemical and thermal stability of the prepared composites. It has been established that, depending on the method of silanization, the composite properties were changed. The obtained experimental results may lead to further research on the functionalization of elastic composites reinforced with magnetic powder.