Abstract It has been demonstrated that the two main subsets of peripheral γδ T cells, Vγ1 and Vγ4, have divergent functions in many diseases models. Recently, we reported that Vγ4 γδ T cells played a protective role in tumor immunity through eomesodermin-controlled mechanisms. However, the precise roles of Vγ1 γδ T cells in tumor immunity, especially whether Vγ1 γδ T cells have any interaction with Vγ4 γδ T cells, remain unknown. We demonstrated in this paper that Vγ1 γδ T cells suppressed Vγ4 γδ T cell-mediated antitumor function both in vitro and in vivo, and this suppression was cell contact independent. Using neutralizing anti–IL-4 Ab or IL-4−/− mice, we determined the suppressive factor derived from Vγ1 γδ T cells was IL-4. Indeed, treatment of Vγ4 γδ T cells with rIL-4 significantly reduced expression levels of NKG2D, perforin, and IFN-γ. Finally, Vγ1 γδ T cells produced more IL-4 and expressed significantly higher level of GATA-3 upon Th2 priming in comparison with Vγ4 γδ T cells. Therefore, to our knowledge, our results established for the first time a negative regulatory role of Vγ1 γδ T cells in Vγ4 γδ T cell-mediated antitumor immunity through cell contact-independent and IL-4–mediated mechanisms. Selective depletion of this suppressive subset of γδ T cells may be beneficial for tumor immune therapy.