ObjectiveTo investigate Vietnamese people’s knowledge, attitudes, and experience in purchasing medicines and functional foods online.MethodsVia an online survey, the data of 1,070 participants were collected, including their general characteristics, Internet use, previous experience, knowledge, and attitudes towards purchasing medicines/functional foods online. Factors associated with their knowledge and attitudes were identified via multivariate linear regression models.ResultsDuring 2022–2023, about 97.2% of participants used the Internet to seek health information (self-diagnosis: 65.0%, self-medication: 72.6%). Roughly 52.8% bought medicines and/or functional foods online. Among 565 buyers, 41.8% felt satisfied. Only 19.9% understood that selling medicines online was illegal in Vietnam. The main benefits of purchasing medicines/functional foods online that many people agreed on included convenience (87.1%), freedom from location (84.8%), and being able to order/buy products after opening hours (84.7%). Many people felt worried about the ability to buy counterfeit or substandard products (87.7%), inaccurate product information (85.0%), the lack of supervision of the authorities (83.7%), and increasing risks of drug abuse, self-medication, and treatment non-adherence (82.5%). Roughly 84.3% found distinguishing between legal and illegal online pharmacies difficult. Participants’ average knowledge and attitude scores were 6.514 ± 2.461 (range: 0–16) and 89.330 ± 13.720 (range: 23–115), respectively. The main factors associated with people’s knowledge and attitudes towards purchasing these products online included their frequency of Internet use, seeking health information online for self-medication, feeling satisfied with previous experience, and having at least one chronic disease.ConclusionsMany Vietnamese people’s knowledge about purchasing medicines/functional foods online was limited. With the increasing need for online shopping, enhancing their knowledge is paramount. In the forthcoming years, when the Ministry of Health and relevant authorities publish legal documents and enact laws involving online pharmacies and trading medicines on the Internet, ways to recognize licensed online pharmacies must be widely propagated and disseminated in the community.