Isoniazid and isoniazid/β-cyclodextrin complexes were prepared in equal molar ratios and their photostability in aqueous solution under room light and UV light exposures were evaluated. An aqueous solution of isoniazid/β- cyclodextrin complexes was prepared using five different methods via co-precipitation, co-evaporation and freezedrying at different temperatures and pH buffer solutions. Stability tests for free isoniazid showed that isoniazid was stable at room temperature (25 °C) and acidic buffer solution. Additionally, β-cyclodextrin slightly enhanced the stability of isoniazid under the tested parameter. Among the tested complexes, the stability effect increased in the following order: co-precipitation > freeze-drying > co-evaporation.