Microbial infections, particularly those caused by emerging and antibiotic-resistant pathogens pose grave threats to human health. As a powerful antibiotic-free strategy, light-triggered therapy offers non-invasive treatment with low side effects, broad antimicrobial spectra and reduced resistance potency. Among various light-responsive antimicrobial agents, fluorescent cationic polyelectrolytes (FCPs) have attracted great attention due to their intrinsic dark toxicity to microbes together with efficient generation capabilities of reactive oxygen species and heat under light irradiation, enabling multifaceted antimicrobial treatment via photodynamic and/or photothermal therapies. This review summarizes the recent advances in the synthesis and light-triggered antimicrobial applications of different types of FCPs, including side-chain fluorescent cationic polyelectrolytes (SFCPs) and main-chain fluorescent cationic polyelectrolytes (MFCPs). The commonly used synthetic routes and structures of SFCPs and MFCPs are discussed in detail. In view of the critical role of positively charged moieties, we further classify FCPs into different groups based on their embedded cationic structures and provide a detailed description on the light-triggered antimicrobial scenarios of SFCPs and MFCPs bearing different cations. Finally, the existing challenges and future perspectives of FCP-based antimicrobial phototherapy are outlined to provide insights for the development of novel FCP bactericides with more diversified structures and advanced functionalities.