Background To investigate the phenotype and function of mucosal-associated invariant T (MAIT) cells in the peripheral blood of patients with Henoch-Schönlein purpura (HSP), owing to the lack of evidence on the role of MAIT cells in HSP. Methods Blood samples from patients with HSP and healthy donors (HDs) were assessed by flow cytometry and single-cell RNA sequencing (scRNA-seq) to analyze the proportion, phenotype, and function of MAIT cells. We analyzed Th-cytokines in the serum of patients with HSP by cytometric bead array (CBA). IgA in cocultured supernatant was detected by CBA to analyze antibody production by B cells. Results We found that the percentage of MAIT cells in patients with HSP was significantly reduced compared with that in HDs. HSP MAIT cells displayed activation phenotype with up-regulated CD69, FOS, and JUN, indicating that these cells were in the early stage of development. HSP MAIT cells also displayed a Th2-like profile with the capacity to produce interleukin (IL)-4 and IL-5. We also demonstrated that IL-4 was correlated with IgA levels in the serum of patients with HSP. Additionally, CD40L was up-regulated in HSP MAIT cells, and CD40L+ MAIT cells showed an enhanced ability to produce IL-4, leading to IgA secretion in patients with HSP. Conclusion Our data demonstrate that MAIT cells in patients with HSP exhibit an activated phenotype. The IL-4 production of CD40L+ MAIT cells in patients with HSP could take part in the pathogenesis of HSP and this finding suggested that targeting MAIT cells may constitute an attractive strategy for HSP.