In this study, we perform in vivo animal experiments on implanted prostatic tumors in mice to measure temperature elevation distribution in the tumor during magnetic nanoparticle hyperthermia. Temperature rises are induced by a commercially available ferrofluid injected to the center of the tumor, which is subject to an alternating magnetic field. Temperature mapping in the implanted prostatic tumors during the heating has illustrated the feasibility of elevating the tumor temperature higher than 50°C using only 0.1 cc ferrofluid injected in the tumor and under a relatively low magnetic field (3 kA/m). Ferrofluid infusion rates during intratumoral injection may affect nanoparticle spreading in tumors. Using a very slow infusion rate of 5 μl/min results in an average temperature elevation in tumors 27°C above the baseline temperatures of 37°C. However, the temperature elevations are barely 14°C when the infusion rate is 20 μl/min. Our results suggest a more confined nanoparticle distribution to the injection site using smaller infusion rates.