Monitoring chemical reactions that occur in small spaces or confined environments is challenging. Surface-enhanced Raman scattering (SERS) spectroscopy offers the unique possibility to monitor spectral changes with high sensitivity and time resolution. Herein, we report the application of composite mesoporous TiO2 films loaded with Ag nanoparticles (NPs) to track in situ chemical processes in real time. In particular, the AgNPs@TiO2 system was employed to monitor two chemical reactions: one occurring on the Ag NPs surface and another taking place in the surrounding solution. In the first case, we monitored the decarboxylation reaction of 4-mercaptobenzoic acid on Ag NPs, which allowed us to identify the conditions that favor it. In the second case, we studied the pH evolution in the nanocavities during a homogeneous alkalization process driven by chloride-assisted glycidol rupture (the Epoxide Route) and compared it with pH measurements by conventional techniques. We therefore demonstrated that the proposed nanodevice provides an excellent performance to monitor dynamic processes occurring either inside the material or in the solution in which it is immersed.