Introduction: The triple burden of malnutrition (TBM) is a growing public health issue worldwide. This study examined the prevalence and association between undernutrition, overnutrition and micronutrient deficiencies (MNDs), and the associated demographic and socioeconomic determinants, among Vietnamese children, using the nationally representative General Nutrition Survey 2020. Methods: Data on anthropometric parameters, micronutrients biomarkers, demographic and socioeconomic indicators for 7,289 children aged 6 months to 9 years old were analysed. Determinants of malnutrition were assessed using logistic regressions and reported as odds ratio (OR) [95% confidence intervals (CI)]. Results: Overall, 12.7%, 10.5% and 4.7% of children were stunted, underweight and wasted/thin; while 7.3% and 7.1% were living with overweight and obesity, respectively. Low serum zinc, anaemia and iron deficiency (ID) were the common MNDs observed, affecting 53.1%, 15.2% and 13.9% of the study participants. Older children aged 2-4 years old [OR (95% CI): 1.43 (1.20, 1.72)], ethnic minorities [5.94 (3.78, 9.36)] and living in mountainous areas [5.06 (1.18, 14.42)] had increased odds of stunting, whereas reduced odds were found in children from the richest quintile [0.13 (0.05, 0.32)]. Similar determinants were found to be associated with underweight and MNDs. Males [1.43 (1.16, 1.76)], children aged 5-9 years old [10.02 (6.71, 14.97) and children from the richest quintile [2.91 (1.20, 7.05)] had increased odds of overweight. Children with anaemia, low serum retinol and low serum zinc had increased odds of stunting and underweight than non-micronutrient deficient children (adjusted OR=1.43-1.71). Compared to children without MNDs, those with ≥3 MNDs had almost double the odds of stunting and underweight, whereas those with ≤3 MNDs had reduced odds of overweight (adjusted OR=0.38-0.60). Conclusions: Significant demographic variation and socioeconomic inequalities in child malnutrition were identified. National policies and programmes in Vietnam should address age-specific, sex-specific, geographical and socioeconomic disparities to accelerate progress in reducing child malnutrition.