Multifunctional nanocomposites based on BaGdF5 nanoparticles (NPs) and metal phenolic network (MPN) have been engineered as novel contrast agents for potential applications in X-ray computed tomography, magnetic resonance and luminescence imaging. The BaGdF5@MPN nanocomposites were synthesized at room temperature by coating BaGdF5 NPs with europium-phenolic network, which was obtained by the coordination of europium (III) with tannic acid (TA). The in vitro cytotoxicity assays against HepG2 cells revealed that the BaGdF5@MPN nanocomposites presented better cytocompatibility and lower cytotoxity than pure BaGdF5 NPs. In addition, vivid red and green luminescence can be observed by confocal laser scanning microscope (CLSM) from the BaGdF5@MPN nanocomposites laden HepG2 cells under the excitation of UV (390 nm) and visible light (440 nm), respectively. The longitudinal relaxivity value (r1) of the nanocomposites was 2.457 mM-1s-1. Moreover, the nanocomoposites exhibited X-ray computed tomography (CT) and T1-weighted magnetic resonance (MR) imaging capacities, and the intensities of the enhanced signals of in vitro CT and MR images were proportional to the concentrations of the nanocomposites. These results indicated that the as-prepared BaGdF5@MPN nanocomposites are promising contrast agents for CT/MR/luminescence imaging.