Poor household dietary diversity has been linked to malnutrition in individuals, households, and cumulatively in populations. High rates of malnutrition among Khmer ethnic children aged five years and younger have been reported in Tri Ton district, Vietnam. This paper aims to further investigate household dietary diversity and associated factors among Khmer ethnic minority populations in Vietnam. A cross sectional study was conducted from October 2018 to April 2019 in Tri Ton District, An Giang Province. By employing a multistage sampling technique, a total of 402 (99.8% response rate) participants were interviewed to measure household dietary diversity using a structured and validated questionnaire developed by FAO. Both bivariate and multivariate logistic regression analyses were carried out to identify factors associated with household dietary diversity. The results showed that the prevalence of low, medium and high dietary diversity scores were 21.4%, 70.4% and 8.2%, respectively. Male-headed households, literacy level, household income, exposure to mass media on nutrition and health information, and frequency of eating were positively associated with household dietary diversity (p < 0.05). However, owning a vegetable and rice farm was not statistically related to households’ dietary diversification. The paper concludes that the magnitude of household diversified dietary intakes was essentially low to medium in participants’ households. These findings have provided evidence to inform the development of the National Nutrition Strategy—2021−2030 in Vietnam, to be revised in 2045. This national strategy proposes appropriate interventions, programs and policies to improve socioeconomic status in ethnic groups and in mountainous areas to enhance populations’ health and well-being including controlling childhood malnutrition. In order to improve population health and wellbeing in Tri Ton District, further actions to address effective dietary practices including strengthening nutrition and health communication about the need to improve household dietary diversity to high levels are recommended.