<p>Collectin Subfamily Member 12 (COLEC12), a C-type lectin family member with collagen-like and carbohydrate recognition domains, remains poorly characterized in pancreatic cancer (PC). COLEC12 expression was analyzed by bioinformatics and immunohistochemistry. Functional assays (CCK-8, colony formation, EdU, flow cytometry, Transwell) and a xenograft model were used to assess its tumor-promoting effects. Mechanistically, transcriptome sequencing, Western blotting, co-immunoprecipitation (Co-IP), molecular docking, truncation mutant mapping, cycloheximide (CHX) chase assay, and ubiquitination assays were performed. The Cancer Genome Atlas (TCGA) data were used for immune infiltration analysis, and quantitative real-time PCR (qRT-PCR) was used to examine the role of COLEC12 in macrophage polarization. Chemosensitivity to gemcitabine and 5-fluorouracil (5-FU) was also evaluated. COLEC12 was upregulated in PC and promoted cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT), while suppressing apoptosis. Mechanistically, COLEC12 directly bound to TGF-β1 via its collagen-like domain, as demonstrated using truncation mutants. CHX chase assays revealed that COLEC12 overexpression delayed TGF-β1 degradation, and ubiquitination assays showed that COLEC12 knockdown increased TGF-β1 ubiquitination, indicating that COLEC12 stabilizes TGF-β1 by suppressing its ubiquitin-proteasome degradation, thereby sustaining activation of the TGF-β/Smad pathway. Furthermore, COLEC12 expression positively correlated with immune cell infiltration levels in TCGA data, and qRT-PCR revealed that COLEC12 expression in PC cells promotes M2 polarization of co-cultured macrophages. Knockdown of COLEC12 increased the sensitivity of PC cells to gemcitabine and 5‑FU. This study reveals, for the first time, the tumor-promoting function of COLEC12 in PC and highlights its potential as a therapeutic target in PC.</p>