Regulatory B cells (Bregs) are a functionally defined B cell subset, and IL-10 is crucial for the suppressive functions of Bregs. However, little is known regarding how IL-10 production is regulated in B cells. To explore the mechanisms by which IL-10 is regulated in B cells, we used mRNA microarrays to screen for molecules that are upregulated in IL-10-producing B cells and identified RNA-binding motif protein 47 (Rbm47) as a post-transcriptional regulator. Rbm47 was found to promote IL-10 production in B cells. We found that Rbm47 promotes the stability of IL-10 mRNA by binding to AU-rich elements in the 3′ untranslated region of Il10 mRNA. In addition, we demonstrated that the overexpression of Rbm47 enabled B cells to facilitate Foxp3⁺ regulator T-cell induction and reduce the severity of DSS-induced ulcerative colitis. Taken together, these results suggest that Rbm47 plays an important role in regulating IL-10 at the post-transcriptional level, thus promoting the regulatory functions of B cells. The findings presented in this study not only increase our understanding of the post-translational regulation of IL-10 in B cells but also identify a novel strategy for the potential application of Bregs.