Backgorund: Superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively used for targeted drug delivery systems due to their unique magnetic properties.In this study, it's aimed to develop a novel targeted 99mTc radiolabeled polymeric drug delivery system for Gemcitabine (GEM).Gemcitabine, an anticancer agent, was encapsulated into polymer nanoparticles (PLGA) together with iron oxide nanoparticles via double emulsion technique and then labeled with 99mTc. SPIONs were synthesized by reduction-coprecipitation method and encapsulated with oleic acid for surface modification. Size distribution and the morphology of the synthesized nanoparticles were caharacterized by dynamic light scattering(DLS)and scanning electron microscopy(SEM), respectively. Radiolabeling yield of SPION-PLGAGEM nanoparticles were determined via Thin Layer Radio Chromatography (TLRC). Cytotoxicity of GEM loaded SPION-PLGA were investigated on MDA-MB-231 and MCF7 breast cancer cells in vitro.SEM images displayed that the average size of the drug-free nanoparticles was 40 nm and the size of the drug-loaded nanoparticles was 50 nm. The diameter of nanoparticles were determined as 366.6 nm by DLS, while zeta potential was found as-29 mV. SPION was successfully coated with PLGA, which was confirmed by FTIR. GEM encapsulation efficiency of SPION-PLGA was calculated as 4±0.16 % by means of HPLC. Radiolabeling yield of SPION-PLGA-GEM nanoparticles were determined as 97.8±1.75 % via TLRC. Cytotoxicity of GEM loaded SPION-PLGA were investigated on MDA-MB-231 and MCF7 breast cancer cells. SPION-PLGA-GEM showed high uptake on MCF-7, whilst incorporation rate was increased for both cell lines which external magnetic field application.99mTc labeled SPION-PLGA nanoparticles loaded with GEM may overcome some of the obstacles in anti-cancer drug delivery because of their appropriate size, non-toxic, and supermagnetic characteristics.