Interleukin 15 (IL-15) is a member of the four-helix bundle cytokine family and has T cell growth factor activity. IL-15 plays a unique role in both innate and adaptive immune cell homeostasis, particularly for the development of NK cells and CD8+memory cells. It may be useful for stimulation of specific immune responses in chronic viral infection such as hepatitis B virus infection. The woodchuck model is an informative animal model for studies on hepadnavirus infection and therapeutic interventions. Here, the complete coding sequence of woodchuck IL-15 (wIL-15) was cloned and sequenced. wIL-15 shows a high homology (>70%) to its counterparts of other mammalian species. His-tagged recombinant wIL-15 protein was expressed and purified and showed the ability to promote the proliferation of activated mouse splenocytes and woodchuck peripheral blood lymphocytes. Further, examination of mRNA amounts in liver samples of woodchucks by semi-quantitative RT-PCR showed a slightly increased expression of wIL-15 in woodchuck livers during chronic woodchuck hepatitis virus infection. This available information will provide a basis for further studies on the function of IL-15 in the context of acute and chronic hepadnavirus infection and its potential therapeutic use for chronic hepatitis B virus infection in the woodchuck model.