ZnAl-LDH(layered double hydroxide) modified with oleic acid(SO-ZnAl LDH) was synthesized and added to the flame retardant ABS compounds containing brominated epoxy resin(BER) and antimony trioxide(${Sb_2}{O_3}$). Flame retardant ABS compounds were manufactured by using a twin-screw co-rotating extruder and subsequently injection molded into several specimen for flame retardancy and mechanical properties. The XRD patterns of ABS nanocomposites showed no peaks. The thermal stability of ABS nanocomposites was enhanced by the addition of SO-ZnAl LDH as shown in TGA results. However, these nanocomposites showed no rating in the UL 94 vertical test at 1.6 mm thickness. Only ABS nanocomposites with additional BER more than 1.5 wt% showed UL 94 V0 rating. Notched Izod impact strength, tensile modulus, and elongation at break of flame retardant ABS nanocomposites increased with the proportion of So-ZnAl LDH whereas their melt index decreased.