This document summarizes a method for preparing polymer-coated magnetic nanoparticles for targeted delivery of drugs to treat brain tumors. Magnetite nanoparticles are first synthesized and then coated with oleic acid. The oleic acid-coated nanoparticles are then encapsulated in poly(DL-lactic-co-glycolic acid) (PLGA) using an oil-in-water emulsion method. This PLGA coating makes the nanoparticles biocompatible and able to pass through the blood-brain barrier to accumulate in tumor tissues via the enhanced permeability and retention effect. The polymer-coated magnetic nanoparticles allow for targeted delivery of drugs to brain tumors while avoiding effects on other tissues.