Antimicrobial Resistance (AMR) happens when microorganisms such as bacteria, viruses, fungi and parasites are able to resist the inhibition or killing effects of medicines used to treat the infections they cause, making drugs ineffective and microorganisms resistant. The misuse or, overuse of antibiotics to treat bacterial infections affecting aquaculture species can speed up the AMR process. This is caused by lack of veterinarian supervision and inadequate laboratory testing methods. WorldFish in close collaboration with Cefas researchers from the UK FAO Reference Centre for Antimicrobial Resistance developed this quick protocol for antimicrobial susceptibility testing (AST) in aquatic animal species from aquaculture and fisheries. This protocol is intended to support and benefit national partners and researchers working in Asia and Africa in the areas of aquatic food systems and One Health and bring harmonization of methodologies across ongoing initiatives.