RNA-binding motif protein 38 (Rbm38), also known as RNPC1, is a major regulator of post-transcriptional gene expression. It represents a potential candidate gene linked to the susceptibility of type 2 diabetes, and decreased RBM38 expression can enhance the proliferation of pancreatic cancer cells in humans. However, its role in pancreatic development remains elusive. In this study, we explored the function of Rbm38 using zebrafish as a model. Pancreatic expression of Rbm38 is present at larval stages and is controlled by several transcription factors acting on specific rbm38 promoter regions. The loss of Rbm38 leads to abnormal pancreatic enlargement. Mechanistically, Rbm38 is involved in several aspects of post-transcriptional regulation of pancreatic gene expression. It destabilizes pdx1 transcripts by binding to the 3′-untranslated region and regulates alternative splicing of key pancreatic transcription factor genes, including isl1a, smad2, and nkx2.2a. These findings elucidate the role of Rbm38 in pancreatic development and highlight its significance in maintaining pancreatic homeostasis.