The chemical wet processing of textiles continues to expand each year using new technologies. The driving force being the need for cleaner, cost-effective and value added textile products. It is well known that, wool fabrics can be colored easily with acid, basic, direct, metal complex and reactive dyes while disperse dyes are used to colorate polyester fabrics. In the present study, wool and wool/polyester fabrics are printed with disperse dye nanoparticles treated by refluxing the particles in nitric acid with two different concentrations for a certain period of time at different temperatures. This treatment results in hydrophobic carboxylic groups on dye nanoparticles surfaces which behave similarly to acid dyes used in printing wool fabrics. Various parameters and measurements involving this work are investigated in detail such as: K/S values, dye particle size, nitric acid treatment conditions, printing paste pH, steaming conditions of the prints, SEM, TEM and FT-IR analysis of dye nanoparticles as well as fastness properties of the prints.