Powders were obtained using an indium chloride solution and were characterized as a function of precipitation pH, aging time, and concentration of the liquid synthetic medium. Indium hydroxide (In(OH)3) and indium oxide hydroxide (InOOH) coexisted in the pH range of 5 to 8, but only indium hydroxide was present at pH 9 and 10. The crystallite size of In(OH)3 had a stronger dependence on pH than on the concentration of the reaction medium compared to InOOH. Hence, the relative crystallite size of In(OH)3 increased significantly with increasing pH compared to that of InOOH, which barely changed with increasing concentration and pH. Although the crystallite size of In(OH)3 increased slightly with increasing precipitate aging time, the specific surface area decreased significantly. These results can help control the synthesis of indium oxide particles used to make indium tin oxide targets.