Porous solids are a rapidly developing class of materials with an ever-increasing range of applications. Among these materials, amorphous porous mixed oxides possess the extraordinary properties of fine tuning the chemical composition, microstructure, porosity and surface properties. The tailor made composition of the mixed oxides can be fabricated from the availability of variety of precursor, additives and modifiers. Besides, their performance can be found close to that of crystalline phase. These amorphous mixed oxides can easily be synthesized using acid / base catalyzed one-pot sol-gel procedure. Sol-gel processes allow for a relatively facile tailoring of the morphology of mixed oxides to the desired application in the field of nanotechnology. Pore volume, porosity, specific surface area, and surface acidity are typical parameters that can be tailored. This chapter deals with the preparation methodology, characterization techniques, and application of amorphous porous mixed oxides.