CLINICAL ONCOLOGY AND RESEARCH Abstract The aim of the current work was to elucidate whether the encapsulation of curcumin in nanoparticles (of microemulsion type) would allow its exertion of anticancer activity on several cancer cell lines or not. Curcumin microemulsion was prepared using the water dilution method, in which oleic acid constituted the oily phase, and tween 20, ethanol constituted the surfactant and cosurfactant respectively. The microemulsion was tested for its particle size, charge, morphology using transmission electron microscopy, in vitro curcumin release, stability and anticancer activity on HCT-116 colon cancer line, A549 lung cancer cell line, and PC3 prostate cancer cell line. The safety of the formulation was tested on fibroblasts cell line. Results revealed that curcumin microemulsion was successfully prepared with a particle size of 11.45±0.21 nm, and a negative charge of -9.07 mV, and it was able to sustain the release of drug for 24 hours with a cumulative percent released of 66.72%. Its spherical morphology was confirmed using transmission electron microscopy. No significant changes in particle size or charge were observed upon storage, suggesting the physical stability of the microemulsion. Curcumin microemulsion was proven safe on the normal fibroblasts cell line, and it preserved the anticancer activity of curcumin against A549, HCT116, and PC3 cell lines. Results of this study delineate that microemulsion is a suitable nanodelivery system for curcumin, which needs to be tested on animal tumor models for verification of the anticancer properties in vivo.