Plant biosecurity threats such as pest, weeds and disease occurrences cause substantial economic damage to the agricultural sector, worldwide and in Australia. How smallholder farmers choose biosecurity management strategies remains poorly understood, particularly of smallholder cultural minority groups. In this study, we explore how Vietnamese smallholder farmers in Australia assess their biosecurity risk management strategies and the factors that explain their choice of different strategies. To do so, we conducted a survey of 101 Vietnamese farmers in the Northern Territory, South Australia and Western Australia. Based on the protection motivation theory, we assessed farmers’ perceived self-efficacy, response efficacy and response costs (all elements of their coping appraisal) using descriptive statistics, factor analysis and stepwise regression. Information sources related to biosecurity and farmers’ trust in public management explain how farmers assess their risk management strategies. Previous experience with biosecurity issues does not influence how farmers appraise their biosecurity risk coping capacity. Farmers use four types of biosecurity risk management strategies: chemical control, plant growth strategies, on-farm strategies and asset investment strategies. The first two are the most frequently used. We recommend tailoring relevant government policies to better support farmers’ adoption of risk management strategies based on their specific needs, more investment into biosecurity information dissemination and into trust building.