Mifepristone, a progesterone receptor antagonist, was initially used to terminate early pregnancy. As scientific research advanced, it emerged to be effective in the treatment of various tumors and tumor-like conditions such as endometriosis. Despite the therapeutic potential of mifepristone, its therapeutic effect is still far from ideal because the drug is difficult to dissolve and to accumulate in the target tissue sites. To address this issue, mifepristone-loaded nanostructured lipid carriers (Mif-NLC) were prepared by a simple solvent diffusion method and their anti-endometriosis performance and mechanisms were initially investigated. By optimizing the preparation protocol, we obtained uniform and spheroidal Mif-NLC with an average particle size of 280 nm. The encapsulation rate and drug loading capacity were 64.67% ± 0.15% and 2.7% ± 0.014%, respectively, as measured by UV spectrophotometry. The in vitro release kinetics indicated that mifepristone was released from NLC in a sustained-release manner. Compared with free mifepristone, Mif-NLC exhibited enhanced cellular uptake and inhibition of invasion activity in primary mesenchymal cells of endometriosis. A certain reduction in the size of endometriotic cysts was observed in animals compared to controls. The induction of autophagy via Mif-NLC may serve as the molecular mechanism underlying this effect. Furthermore, observation of uterine structures showed negligible toxic effects. This suggested that mifepristone encapsulated in NLC can improve its bioavailability and anti-endometriosis efficacy, which provided a new strategy for the treatment of endometriosis.