Interleukin-15 (IL-15), natural killer (NK) cells, and NK T (NKT) cells, components of the innate immune system, are known to contribute to defense against pathogens, including viruses. Here we report that IL-15^−/− (NK⁻ and NKT^−/+) mice and RAG-2^−/−/γ_c^−/− (NK⁻ and NKT⁻) mice that lack all lymphoid cells were very susceptible to vaginal infection with a low dose of herpes simplex virus type 2 (HSV-2). IL-15^−/− and RAG-2^−/−/γ_c^−/− mice were 100-fold more susceptible and RAG-2^−/−, CD-1^−/− (NKT⁻), and gamma interferon (IFN-γ)^−/− mice were 10-fold more susceptible to vaginal HSV-2 infection than control C57BL/6 mice. NK and/or NKT cells were the early source of IFN-γ in vaginal secretions following genital HSV-2 infection. This study demonstrates that IL-15 and NK-NKT cells are critical for innate protection against genital HSV-2.