We report on a facile route for the immobilization of silver nanoparticles (Ag NPs) onto the pH-responsive poly(2-vinylpyridine) (P2VP) brushes. The process involves chemical grafting of P2VP chains on the underlying substrate in brush conformation followed by the in situ synthesis of Ag NPs via chemical reduction of silver nitrate (AgNO3) in the presence of P2VP brushes. The effect of various reaction parameters, such as the employed concentration of AgNO3 salt and reduction time on the immobilization process, has been demonstrated. The quantitative analysis of the loaded amount and surface coverage of the Ag NPs on polymer brushes as a function of the employed AgNO3 salt concentration has been discussed. Immobilization of Ag NPs onto the P2VP brushes has been confirmed by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-vis) spectroscopy. Finally, the system was used to fabricate the nanosensors for detecting the pH of surrounding aqueous medium. The concept is based on the variation in surface plasmon resonance of immobilized Ag NPs with changing the interparticle distances, caused by the swelling/deswelling of the responsive polymer brushes.