Monoclonal antibodies (MAbs) are now among the crucial tools for diagnosing and controlling pathogens in fish and shrimp, playing a vital role in health management aquaculture. This chapter explores the wide applicability of MAbs, especially underlining their importance in pathogen detection and disease prevention. It describes the concept as well as the advantages of MAbs, their specificity, reproducibility, and flexibility in diagnostic and therapeutic applications. Therapeutic applications of MAbs in human medicine provide a paradigm for their potential applications in fish health. In aquaculture, MAbs are widely employed in detecting pathogens, following immune responses, and developing vaccines. Key developments are highlighted, including the generation of MAbs against serum immunoglobulins of finfish, bacterial pathogens, and viral pathogens. Details of similar applications in shrimp aquaculture are also provided, with emphasis on bacterial and viral pathogens. The general protocol for the production of MAbs is covered in this chapter, including antigen preparation, hybridoma technology, and MAb purification. Further, an optimized protocol for indirect ELISA is provided, which illustrates its use in detecting pathogen-specific antibodies and antigens. The chapter verifies the possibility of revolutionizing pathogen detection and, hence, disease control in aquaculture with MAbs. The chapter presents a call for further research towards the development of expanding MAb applications to include therapeutic intervention as well as rapid diagnostic tools, thereby ensuring sustainable aquaculture with better fish health. The comprehensive overview provides solid foundation insights to researchers, diagnosticians, and practitioners.