This study aimed to determine the effect of calcination time on the properties of Al(OH)3 or gibbsite nanoparticles in the sol-gel process, which was then used as the basic material in the manufacturing of water-Al(OH)3 based nanofluids. Nanofluid is a mixture of basic fluids such as water with solid nanoparticles. Al(OH)3 nanoparticles have been successfully synthesized from Indonesia local mineral bauxite using the sol-gel method by utilizing tomato waste extract as a chelating agent at a calcination temperature of 700ºC for 1 hour, 3 hours, and 5 hours. The obtained calcined powders were characterized using X-ray diffractometer (XRD). The evaluation toward nanofluids application based on theirs stability based on visual observation and zeta potential. Based on XRD analysis, all calcined powders has single Al(OH)3 or gibbsite phase. Increasing the calcined temperature gave impact on crystallinity, crystallite size, and reorientation of crystal. The water-Al(OH)3 nanofluid was relatively less stable with a zeta potential value of -25.2 mV; -26.4 mV; and -17.4 mV for calcination time 1 h, 3 h, and 5 h, respectively.