This study is unique in studying the thermogravimetric analysis (TGA) of poorly water-soluble drugs before their formulation. Three selected drugs atorvastatin, albendazole and diclofenac were mixed with three different polymers hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP) and soluplus (SOL). The pure drugs and physical mixtures were subjected to solvent evaporation and milling techniques to obtain solid dispersions. All, as received and TGA analyzed solid dispersion mixtures to evaluate their thermal behavior at a temperature that ranged from 0–300°C. The results showed that the addition of polymer either in physical mixtures or solid dispersions of the drugs has resulted in either increase or decrease of the thermal stability of the drugs depending on the method of preparation and the type of the polymer and the nature of the drug.