Several studies suggested that interleukin (IL)-15 is a promising adjuvant of human immunodeficiency virus (HIV) vaccine via promoting cellular immunity. Here we evaluated the effect of IL-15 plasmid on HIV specific immune response, especially cellular immunity, in 8 rhesus monkeys. These monkeys were immunized three times with HIV DNA vaccine with or without IL-15 plasmid, and boosted with recombinant Tiantan strain vaccinia virus-based HIV vaccine (rTV) 22 weeks after the first immunization. As the results, the percentages of effector CD8 + memory T cells in the peripheral blood were significantly higher in the group with IL-15 co-immunization (Group T) than those in the group with HIV vaccine alone (Group C) at almost all the time points, while no significant difference in HIV specific CD8 + T cells response was found between Group T and Group C throughout the experiment. The titers of anti-HIV antibodies were higher in Group T than those in Group C after rTV boosting as well. These findings in rhesus monkeys suggest that IL-15 may be used as a cytokine adjuvant for HIV vaccine.