AbstractVγ9/Vδ2 T cells are a minor subset of T cells in human blood and differ from all other lymphocytes by their specific responsiveness to (E)‐4‐hydroxy‐3‐methyl‐but‐2‐enyl pyrophosphate (HMB‐PP), a metabolite produced by a large range of microbial pathogens. Vγ9/Vδ2 T cells can be skewed towards distinct effector functions, in analogy to, and beyond, the emerging plasticity of CD4+ T cells. As such, depending on the microenvironment, Vγ9/Vδ2 T cells can assume features reminiscent of Th1, Th2, Th17 and Treg cells as well as professional APCs. We here demonstrate that Vγ9/Vδ2 T cells express markers associated with follicular B helper T (TFH) cells when stimulated with HMB‐PP in the presence of IL‐21. HMB‐PP induces upregulation of IL‐21R on Vγ9/Vδ2 T cells. In return, IL‐21 plays a co‐stimulatory role in the expression of the B‐cell‐attracting chemokine CXCL13, the CXCL13 receptor CXCR5 and the inducible co‐stimulator by activated Vγ9/Vδ2 T cells, and enhances their potential to support antibody production by B cells. The interaction between HMB‐PP‐responsive Vγ9/Vδ2 T cells, IL‐21‐producing TFH cells and B cells in secondary lymphoid tissues is likely to impact on the generation of high affinity, class‐switched antibodies in microbial infections.