This study aimed to identify the protein composition of mucus in Crassostrea gigas (Pacific oyster) and analyze the proteomic changes during Vibrio ZJ-51 infection. Mucus samples were collected from control (C1–C3) and infected oysters (T1–T3). Using LC-MS/MS, over 4000 proteins were identified from oyster mucus. Differential expression analysis revealed significant proteomic alterations in response to Vibrio infection, providing insights into the host-pathogen interaction and potential defense mechanisms. This study contributes to the understanding of oyster mucus composition and its response to bacterial challenge.