Nano-clay-based composites have increased application in many areas like structural applications, automobiles, medical applications, and the packaging industry in recent decades being low-cost fillers as well as due to several advantages over other fillers. Silane acts as a coupling agent between inorganic fillers and organic matrices. In the present work, the most popular natural clay montmorillonite nano clay (MMT) having a 2:1 structure of the layered sheet of silica and alumina, meaning that an octahedral sheet of alumina is sandwiched between two tetrahedral sheets of silica, was silane functionalized with the help of 3-aminopropyltriethoxysilane (APTES) and double deionized water solvent. The reaction time was varied (½ hour, 3 h, and 24 h) and corresponding silane grafting was calculated from the thermogravimetric analysis (TGA) plot for optimization of reaction time. The 3 h reaction time gives maximum silane grafting. Epoxy nanocomposites were prepared by mixing diglycidyl ether of bisphenol A (DGEBA) epoxy system and clay by mechanical stirring and mold forming to give dog-bone samples. Samples were prepared using functionalized clay with optimized reaction time as well as pristine clay with 2% clay loading. The tensile test was performed for functionalized MMT clay-loaded epoxy nanocomposite, pristine clay epoxy nanocomposite, and neat epoxy samples. The tensile strength and stain at fracture were found to improve in the case of functionalized MMT clay.