Oncolytic herpes simplex virus (HSV) can replicate in and kill cancer cells without harming normal tissue. G47Δ is a third-generation HSV vector. In this study, the therapeutic effects of G47Δ on human nasopharyngeal carcinoma (NPC) were determined in vitro and in vivo. The human NPC cell lines CNE-2 and SUNE-1, primary normal nasopharyngeal epithelial cells (NPECs), and immortalized nasopharyngeal cells NP-69 and NPEC2/Bmi1 were infected with G47Δ at different multiplicities of infection (MOIs). The survival of infected cells was observed daily. Two subcutaneous models of NPC were established with CNE-2 and SUNE-1 in Balb/c nude mice. G47Δ or virus buffer as control was injected into the subcutaneous tumors. Tumor size was measured twice a week, and animals were euthanized when the diameter of their tumors exceeded 18 mm or when the animals appeared moribund. For the NPC cell lines CNE-2 and SUNE-1, more than 85% and 95% of cells were killed on day 5 after G47Δ infection at MOI = 0.01 and MOI = 0.1, respectively. Similar results were observed for an immortalized cell line NPEC2/Bmi-1. A moderate effect of G47Δ was also found on another immortalized cell line NP-69, of which only 27.7% and 75.9% of cells were killed at MOI = 0.01 and MOI = 0.1, respectively. On the contrary, there was almost no effect observed on NPECs. The in vivo experiments showed that tumors in mice in the G47Δ-treated group regressed completely, and the mice exhibited much longer survival time than those in the control groups. Our results suggest that the potential therapeutic effects of G47Δ would be applicable for treatment of NPC patients in the future. G47Δ is a third-generation HSV vector. In this study, the therapeutic effects of G47Δ on human nasopharyngeal carcinoma (NPC) were determined in vitro and in vivo. The human NPC cell lines CNE-2 and SUNE-1, primary normal nasopharyngeal epithelial cells (NPECs), and immortalized nasopharyngeal cells NP-69 and NPEC2 / Bmi1 were infected with G47Δ at different multiplicities of infection (MOIs). The survival of infected cells were observed daily. Two subcutaneous models of NPC were established with CNE-2 and SUNE-1 in Balb / c nude mice. G47Δ or virus buffer as control was injected into the subcutaneous tumors. Tumor size was measured twice a week, For the NPC cell lines CNE-2 and SUNE-1, more than 85% and 95% of cells were killed on day 5 after G47Δ infection at MOI = 0.01 and MOI = 0.1, respectively. Similar results were observed for an immortalized cell line NPEC2 / Bmi-1. A moderate effect of G47Δ was also found on another immortalized cell line NP-69, of which only 27.7% and 75.9% of cells were killed at MOI = 0.01 and MOI = 0.1, respectively. On the contrary, there was almost no effect observed on NPECs. The in vivo experiments showed that tumors in mice in the G47Δ-treated group regressed completely, and the mice exhibit much longer survival time than those in the control groups. Our results suggest that the potential therapeutic effects of G47Δ would be applicable for treatment of NPC patients in the future.