For over eight decades, antibiotics have been the cornerstone of treating bacterial infections. However, the rapid rise of antibiotic-resistant pathogens has created an urgent need for alternative therapeutic strategies. Advances in nanotechnology offer a promising solution through the development of bio-derived nanoparticles. This broad class includes extracellular vesicles such as exosomes and bacterial outer membrane vesicles (OMVs), as well as bioengineered cell membrane-coated nanoparticles (CMNPs) that combine synthetic cores with natural membranes from diverse source cells. These particles possess unique physicochemical and biological properties, such as intrinsic bioactivity, biocompatibility, and structural versatility, that can be harnessed for antimicrobial therapy. This review synthesizes recent progress in the design, characterization, and application of biological nanoparticles for combating bacterial infections. We place particular emphasis on their mechanisms of action, therapeutic potential, and key research directions that could accelerate their translation into clinical use.