Aquaculture production is increasing in Vietnam, but is hampered by frequent disease outbreaks and widespread use of various compounds used to treat the fish and shrimp. The objective of this study was to analyse factors influencing farmer use practices of antimicrobials and other compounds by a questionnaire and observational survey conducted with 60 whiteleg shrimp (Litopenaeus vannamei) and 25 fish farmers in three coastal provinces in Northern Vietnam. Personnel in 22 shops distributing feed and chemicals for aquaculture were interviewed about their advice on sale to the farmers. Results showed that 20 different antimicrobial products were used for disease prevention and treatment in shrimp and marine fish culture. Banned products used included chloramphenicol, enrofloxacin and malachite green. Cage fish farmers said they purchased antimicrobial tablets readily available at a local pharmacy and sold for human use. Chinese traders were the main drug suppliers to the shrimp farmers in Quang Ninh and others provinces. Their products were sold with labels and product information written in Chinese only. Farmers appeared to have little awareness and concern about the disease aetiology when applying specific antimicrobials. Up to 50% of the shrimp farmers used up to 20 different disinfectants, e.g. chlorine-based compounds, to disinfect water in storage ponds, often without knowledge of the type of disinfectants and their mode of action. A variety of probiotics, vitamins, minerals and herbal extracts were routinely used by mainly shrimp farmers to enhance shrimp immunity. There is an urgent need to provide aquaculture farmers access to diagnostic and independent disease control advisory services and quality medicated feed, since the current indiscriminate use of antimicrobials and other compounds are inefficient, costly, and hazardous to the aquatic animal and farmer's health, the environment and food safety.