CBLCIPKs are universal proteins in higher plants that decode Ca²⁺ signals. Base on the previous work, a series of investigations of BnaCIPK15 gene in Brassica napus L., including subcellular localization, bimolecular fluorescence complementation (BiFC), yeast twohybrid (Y2H) and qRTPCR, were carried out to explore its role in ABA hormone response. (1) Subcellular localization result showed that BnaCIPK15 protein was localized in the cytoplasm and nucleus. BiFC assay demonstrated that BnaCIPK15 interacted strongly with BnaCBL1/3/4/9 proteins, and interacted weakly with BnaCBL10 protein as well. (2) Using qRTPCR, the expression pattern of BnaCIPK15 gene was examined under various phytohormone and abiotic stress treatments, and the results revealed that abscisic acid (ABA) and cold stress significantly induced its expression. Moreover, a mild upregulation of BnaCIPK15 gene was also observed by paraquat, reactive oxygen species (H₂O₂) burst and heat stress treatments, suggesting that BnaCIPK15 gene may be involved in the regulation of ABA and cold stress. (3) Y2H assay discovered that BnaCIPK15 protein interacted with BnaHAB1, which belongs to the protein phosphatase type 2C family negatively regulating ABA signaling pathway, and did not show any evident interaction with BnaABFs/AREB3/ABI5 transcription factors. At the same time, BiFC assay also showed that there were interaction signals between BnaCIPK15 and BnaHAB1 proteins, rather than BnaHAB2 protein, which proved that they had specific interaction, suggesting that BnaCIPK15 protein might be involved in regulating ABA signal transduction. In conclusion, this study identified that BnaCIPK15BnaHAB1 module may be involved in ABA signal transduction and regulatory network in Brassica napus.