P-glycoprotein (P-gp) is a membrane-bound efflux pump which actively exports a wide range of compounds from the cell and is associated with the phenomenon of multidrug-resistance. However, the role of P-gp in normal physiological processes remains elusive. Using P-gp deficient fibroblasts, we showed that P-gp was critical for the replication of the intracellular parasite Toxoplasma gondii, but was not involved in invasion of host cells by the parasite. Importantly, we found that the protein participated in the transport of host-derived cholesterol to the intracellular parasite. T. gondii replication in P-gp deficient host cells not only resulted in reduced cholesterol content in the parasite but also altered its sphingolipid metabolism. In addition, we found that different levels of P-gp expression modified the cholesterol metabolism in uninfected fibroblasts. Collectively our findings reveal a key and previously undocumented role of P-gp in host-parasite interaction and suggest a physiological role of P-gp in cholesterol trafficking in mammalian cells.