Spray drying is increasingly becoming recognized as an efficient drying and formulation technique for pharmaceutical and biopharmaceutical processing. It offers significant economic and processing advantages compared to lyophilisation/freeze-drying techniques even though the optimisation of process parameters is often a costly and time-consuming procedure. Spray Drying has primarily been used in formulating small molecule drugs with low solubility however it is increasingly being applied to the processing of large biomolecules and biopharmaceuticals. This review examines the basics of spray drying process, current technology and various components used in spray drying process. Moreover, it is focused on introducing critical formulation and processing factors in spray drying of small molecule drugs and large biomolecules, their similarities and differences. Finally, it provides an overview of the experimental optimisation strategies designed to achieve optimum spray drying results in the shortest possible timeframe while utilising minimum product.