Despite the beneficial effects of ultraviolet (UV) radiation on the skin, radiation can cause sunburn, skin aging, allergies and even skin cancer. Textiles can provide effective protection against such damage. Unlike cosmetics, using textiles to protect the skin has only recently been researched. The design and modification of fabrics leading to a high protection against UV radiation is a relatively new application. It is important to consider the kinds of textiles to be used because most of the garments worn during summer, the time of highest exposure, are light and colourless materials that provide the lowest protection. Here, we report the synthesis and characterisation of nanosized zinc oxide particles known to absorb UV light. Sol-gel-based inorganic-organic hybrid polymers were modified with these particles and applied to cellulosic cotton (100%) and cotton/polyester (65/35%) fabrics. These modified inorganic-organic hybrids polymers were based on 3-GPTMS. The complete finishing sol prepared in this work has a marked long stability. The effectiveness of the novel finishing was determined by UV-visible spectroscopy to evaluate the UV protection factor. The influences of the finishing for general textile properties such as tensile strength, elongation, air permeability, degree of whiteness, wear resistance, stiffness and the durability of the treatments were investigated.