Gibbsite ore used in this study is from Gabal Um Karasi, Southwestern Sinai, Egypt. This gibbsite deposit contains 47.47% Al2O3 and 400 ppm uranium. So, it is considered as a feed material for aluminum and uranium recovery. In this paper, the leaching of aluminum and uranium by sulfuric acid is reported for both calcined and uncalcined samples under different leaching conditions. From the experimental results, it is observed that the leaching efficiency of uranium is largely dependent upon acid concentration and temperature. At 6 mol dm-1 sulfuric acid concentration, the leaching efficiencies´ reached 68% and 98% for aluminum and uranium respectively. The maximum leaching efficiency for both aluminum and uranium reached 98% at 90°C and 1.5 mol dm-1 sulfuric acid. The time of mixing had a great effect on the leaching process where the highest efficiency was observed after 6 hrs stirring time. When the leaching experiments were applied on calcined samples, 98% leaching efficiency was obtained after 3 hrs stirring time, at 95°C and 4 mol dm-1 H2SO4.