Statins possess antitumor actions at doses 100- to 500-fold higher than those needed to lower cholesterol levels. Thus, the antitumor efficacy of statins could be improved greatly by using tumor-targeted delivery systems. Therefore the present work aims to investigate the antitumor activity of long-circulating liposome-encapsulated simvastatin (LCL-SIM) versus free SIM in B16.F10 murine melanoma-bearing mice. Our results showed that LCL-SIM inhibits strongly the B16.F10 melanoma growth (by 85%) whereas free SIM was ineffective. Moreover, the antitumor activity of LCL-SIM depends on the presence of functional tumor-associated macrophages (TAM) in tumor tissue and is mainly based on the reduction of the TAM-mediated oxidative stress as well as of the production of the hypoxia-inducible factor 1 α (HIF-1 α) in tumors. In conclusion, our findings suggest that the antitumor activity of LCL-SIM on B16.F10 melanoma growth is a result of the tumor-targeting property of the liposome formulation and is tightly dependent on the presence of TAM in tumor tissue.