Peripheral follicular helper T (pTfh) cells represent specialized CD4(+)T cells that help B cells to secrete antibodies. Dengue infection appears to cause immune activation in a wide array of immune cells. Herein, we investigated the signatures of immune activation of circulating Tfh cells and mucosal-associated invariant T (MAIT) cells in adult subjects with confirmed acute clinical dengue virus (DENV) infection by multiparametric flow cytometry. The acute DENV infection induced a significant expansion and activation of pTfh cells and circulating MAIT cells during acute febrile infection. We found a higher frequency of activated PD-1(+)Tfh cells and CD38(+)pTfh cells in clinical DENV infection. We also found similar activated and expanding phenotypes of MAIT cells in the patients tested. The numbers of activated pTfh cells and circulating MAIT cells were higher in dengue patients relative to healthy controls. We concluded that pTfh cells and circulating MAIT cells represent activated phenotypes in acute DENV infection.