Nanocomposites of semiconducting two-dimensional (2D) materials provide advantageous for combating bacterial infections to overcome antibiotic resistance. In this study, the nanocomposites of 2D black phoshorus (BP) and silver nanoparticles (NPs) were prepared by anchoring as-synthesized Ag NPs on few-layer BP nanosheets via liquid self-assembly method and used as a NIR-light-driven antibacterial agent against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and Gram-positive bacteria (Enterococcus faecalis and Bacillus cereus). The BP/Ag nanocomposites showed excellent photothermal effect and oxidative stress ability to inhibit the initial logarithmic growth phase of E. faecalis and B. cereus. According to the bacterial growth curve, agar plate assay and live/dead viability test, as-synthesized BP/Ag nanocomposites were found to be more effective antibacterial agent for Gram-positive bacteria than Gram-negative bacteria. The presented NIR-light-driven BP-based nanoplatform can open a new avenue for avoiding bacterial resistance and combating pathogenic bacteria and also broad-spectrum disinfection applications.