Antimicrobial resistance (AMR) is a global public health risk that could be exacerbated by aquaculture. To effectively address this issue, it is essential to implement AMR surveillance within aquatic systems. The sensitivity, specificity, and traceability of modern molecular diagnostic technologies for AMR make it possible to undertake targeted control measures, such as detecting and quantifying specific infections and associated resistance genes. However, these techniques have limitations, including the need for highly trained technicians to carefully operate expensive and time-consuming equipment that carries the danger of producing false-negative and false-positive results. Effective diagnostic approaches are essential for surveillance to understand the origins and spread of AMR. Despite the promising future of these, we must carefully assess their benefits and drawbacks to find the best approach consistent with the goals of each surveillance program. Insights gained from this will ultimately enhance mitigation methods, helping us to fight AMR in aquaculture. The present chapter aims to summarize culture-based, molecular, and phenotypic methodologies included in AMR surveillance programs for aquaculture, recognizing that the use of specific diagnostic tools for such purpose is not without its own merits and limitations.