Antibiotic therapy is the first choice for the treatment of bacterial infections in the clinic. However, the continuously increasing bacterial resistance makes traditional antibiotic therapy difficult to achieve ideal therapeutic performance, necessitating the development of new antibacterial strategies. Polymeric nanoparticles have received much attention in biomedical applications. They can be used as nanocarriers to deliver a variety of antibacterial agents to the infected area. Compared to traditional drug delivery systems, polymeric nanoparticles show various advantages, including improved drug stability, long circulation time, controlled drug release, selective drug accumulation, and so on. This review summarizes the current applications of polymeric nanoparticles for the delivery of antibacterial agents. First, an extensive review of the applications of polymeric nanoplatforms in the delivery of various antibacterial drugs is conducted. The mechanisms and strategies of various stimuli-responsive polymeric nanoplatforms are then discussed, especially focusing on how to improve the antibacterial efficacy and reduce the side effects. Finally, the challenges of future developments of polymeric nanoplatforms in the delivery of antibacterial agents are discussed.