Background: Poly(lactic-co-glycolic acid) (PLGA) is a biodegradable and biocompatible polymer which is widely used as a matrix to incorporate therapeutic agents. The anticancer activity of targeted folate-modified docetaxel-loaded PLGA nanoparticles (F-NP-Doc) was studied in vitro. Methods: Nanoparticles were prepared by a single-emulsion solvent-evaporation technique and characterized by physico-chemical methods. Cell survival was measured by the MTT assay and the sulforhodamine B assay. Folate receptor α expression, particle uptake and apoptosis were assessed by flow cytometry. Results: Folate-modified docetaxel-loaded PLGA nanoparticles showed high anticancer activity in vitro against HeLa cervical carcinoma cells and MCF7 breast adenocarcinoma cells overexpressing folate receptors. Targeted F-NP-Doc nanoparticles were more active compared to free docetaxel and non-targeted NP-Doc nanoparticles; in contrast, the activity of targeted nanoparticles against human fibroblasts (negative control) was significantly lower. F-NP-Doc particles, like free docetaxel, induced apoptosis in cancer cells. F-NP-Doc, but not unmodified docetaxel-loaded PLGA nanoparticles, reversed multidrug resistance of MCF7 R breast adenocarcinoma cells. High antitumor activity of F-NP-Doc has also been proven in in vivo experiments. Conclusions: The summarized experimental data brought us to the conclusion that the incorporation of docetaxel into the targeted PLGA nanoparticles dramatically improves its selectivity against cancer cells.