Antibiotic resistance (ABR) is one of the greatest global health concerns. The growth of food animal farming has challenged efforts to reduce unnecessary antibiotic use (ABU) and is linked to the rapid increases in ABR. This mixed-methods sociological study was conducted between 2016 and 2017, in a sample of 100 animal farmers in southern Vietnam, aiming to characterize their perception of ABU and identify factors influencing their practice. Data were collected from a structured questionnaire investigating characteristics of social demographics and farm style, farmers’ ABU perception and practices, sources of ABU information and the intention to reduce ABU. Generalized linear models were built to investigate potential influencing factors associated with ABU perception and practices. The results show a majority of farmers had an unfavourable perception of ABU. Only 13% correctly knew antibiotics were used for treating bacterial infections. The inappropriate practice of ABU for non-therapeutic purposes was found in almost two-thirds of the farmers (59.4%). Data from the multivariate analysis showed: (1) a significant association between an unfavourable perception of ABU and inappropriate practices, (2) an inverse influence of participation in training workshops to a favourable perception of ABU, but also (3) an inverse influence of participation in training workshops to inappropriate practices of ABU. The results suggest that the local training events that are usually put on by commercial companies do not assist farmers to effectively reduce ABU. On the contrary, these events seem to promote their use. We recognize the complexity of effectively managing appropriate ABU on farms in order to reduce ABR in Vietnam. We conclude that legislation and enforcement needs to be tightened to reduce sale of antibiotics to farmers without veterinarian prescription, and advertising and influence of commercial stakeholders needs to be highly moderated so that they do not unduly promote the unregulated use of antibiotics on farms. Household farmers are important stakeholders in the efforts to reducing ABU and preventing ABR, and therefore should be engaged more effectively.