This research is aimed to perform a symmetric investigation regarding organoclay effect on mechanical behaviors of the glass/epoxy/organoclay nanocomposites. To demonstrate the organoclay effect, three different loadings, 2.5, 5 and 7.5 wt% of organoclay were dispersed in the epoxy resin using mechanical mixer followed by sonication. The corresponding glass/epoxy nanocomposites were prepared by impregnating the organoclay epoxy mixture into the dry glass fiber through a vacuum hand lay-up process. From the tensile tests, it was revealed that the longitudinal tensile strength decreases as the organoclay loading increases, on the other hand, the transverse tensile strength increases with the increases of the organoclay. Furthermore, SEM observation on the transverse failure specimens indicates that the enhancing mechanism is due to the improved interfacial bonding between the fibers and the surrounding matrix modified by organoclay. The similar tendency was also found in the transverse flexural strength of the composites. However, from the mode I fracture tests, it was revealed that with the increase of the organoclay, the corresponding fracture toughness of the composites declines appreciably.