The purpose of this work is to combine magnetite nanoparticles with radioiodinated diethylstilbestrol-glucuronide (DESG) to get a prostate cancer agent. Magnetically targeted drug delivery by particulate carriers is an efficient method of delivering drugs to localized and targeted disease sites, such as tumors. Estrogen glucuronide derivative; DESG was synthesized which is specific for beta glucuronidase enzyme consisting tumor cells and conjugated with iron oxide nanoparticles (NP) and radioiodinated with I-125/131 to evaluate in vitro/in vivo radiopharmaceutical potential of NP conjugated DESG (NP-DESG) and magnetic field applied NP-DESG (MNP-DESG). According to cell culture studies, incorporation ratios of MNP-DESG were higher in MCF7 cells than A549 and Caco2 cells. Biodistribution experiments were verified that the range of the breast/blood and breast/muscle ratios was approximately between 1.82 and 10.10 in 240 min for ER unsaturated studies. The results are promising for targeted therapy of both estrogen receptor and enzyme beta-glucuronidase rich cancers.