The purpose of this study is to develop and evaluate a self-microemulsifying drug delivery system (SMEDDS) to improve the oral absorption of poorly water-soluble olaparib. Through the solubility test of olaparib in various oils, surfactants and co-surfactants, pharmaceutical excipients were selected. Self-emulsifying regions were identified by mixing the selected materials at various ratios, and a pseudoternary phase diagram was constructed by synthesizing these results. The various physicochemical properties of microemulsion incorporating olaparib were confirmed by investigating the morphology, particle size, zeta potential, drug content and stability. In addition, the improved dissolution and absorption of olaparib were also confirmed through a dissolution test and a pharmacokinetic study. An optimal microemulsion was generated in the formulation of Capmul®MCM 10%, Labrasol®80% and PEG 400 10%. The fabricated microemulsions were well-dispersed in aqueous solutions, and it was also confirmed that they were maintained well without any problems of physical or chemical stability. The dissolution profiles of olaparib were significantly improved compared to the value of powder. Associated with the high dissolutions of olaparib, the pharmacokinetic parameters were also greatly improved. Taken together with the results mentioned above, the microemulsion could be an effective tool as a formulation for olaparib and other similar drugs.