The influence of processing variables was experimentally studied for glass fiber reinforced epoxy–clay nanocomposites manufactured using vacuum-assisted wet layup method. The tensile strength, flexural strength, and interlaminar shear strength of these nanocomposites were significantly influenced by the processing variables including the temperature of resin–clay mixture, speed of homogenization, and ultrasonic probe amplitude during premixing of clay minerals in epoxy. The glass transition temperature of glass fiber reinforced composites increased with incorporation of clay minerals in epoxy. Also, the postcuring of the laminates was carried out at three different temperatures, e.g. 100, 130, and 150 ℃ for 3 h. A decrease in tensile modulus, tensile strength, and flexural strength of nanocomposites postcured at 130 and 150 ℃ was observed. Also, the use of non-stoichiometric epoxy resin and hardener ratios had an adverse effect on mechanical properties of fiber reinforced epoxy–clay nanocomposites. In fiber reinforced composites incorporating clay minerals, a uniform dispersion of clay minerals besides a strong interfacial adhesion between clay minerals and polymer and optimum conditions of curing of matrix is a crucial aspect for improved performance over conventional fiber reinforced composites. © IMechE 2018.