MicroRNAs (miRNAs) have been demonstrated that play a critical role in tumorigenesis. The aim of this study is to identify the functional role of miR-378 in cholangiocarcinoma (CCA). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the expression levels of miR-378 in human CCA tissue samples and CCA cell lines. The receiver operating characteristic (ROC) curve was established, and the area under the ROC curve (AUC) was calculated to estimate the capacity of miR-378 in distinguishing CCA patients with different TNM stages. Kaplan-Meier survival analysis and Cox regression assay were performed to explore the prognostic value of miR-378. Cell proliferation capacity was assessed by MTT assay. Cell migration and invasion were identified by Transwell assays. miR-378 was significantly elevated in CCA tissues when compared with adjacent normal tissues, and in CCA cell lines compared to HIBEC cells. And we found that the expression of miR-378 was significantly associated with TNM stage (P= 0.030) and lymph node metastasis (P= 0.018). ROC curve analysis result showed miR-378 could distinguish CCA patients with TNM stages III and IV from those with stages I and II, with the AUC was 0.816. Patients with high expression of miR-378 had a shorter overall survival rate (Log-rank P= 0.030). The miR-378 was proven to be an independent prognostic predictor for the CCA patients (HR = 1.735, 95% CI = 1.007-2.988, P= 0.041). Downregulation of miR-378 could inhibit cell proliferation, migration, and invasion. These results indicated that miR-378 function as an oncogene and promote CCA cells proliferation, migration, and invasion. The miR-378 could be a novel prognostic marker for CCA.