Camellia japonica (common camellia or Japanese camellia) has long been valued in Eastern medicine and cosmetics for its rich bioactive compounds, known for their antioxidant, antimicrobial, anti-inflammatory, and anticancer properties. This study investigated the antibacterial potential of hydromethanolic extracts from leaves and flowers of the 'Lipstick' cultivar against two significant phytopathogens: Erwinia amylovora (EA) and Xanthomonas campestris pv. campestris (Xcc). Gas chromatography-mass spectrometry analysis revealed the primary constituents in the leaf extract to include D-fucose, dihydroxyacetone, methoxy-phenyl-oxime (MPO), 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP), and 1-(4-hydroxy-3,5-dimethoxy phenyl)-ethanone. The flower extract shared MPO and DDMP as main phytochemicals, along with diethoxyacetic acid ethyl ester, nonanoic acid, 1,2-cyclopentanedione, and eicosane. In vitro assays demonstrated low activity for the leaf extract and minimum inhibitory concentration (MIC) values of 1000 and 1250 μg/mL against Xcc and EA, respectively, for the flower extract. At these concentrations, the flower extract achieved complete inhibition of biofilm formation and, in the case of EA, substantial reduction in amylovoran production. Moreover, in vivo tests on artificially-infected Pyrus communis L. branches showed effective control of fire blight at a concentration of 1250 μg/mL. These findings highlight the potential of C. japonica flower extracts as eco-friendly biorationals for protecting crops against bacterial phytopathogens, particularly in the management of fire blight in pear trees.