A cross-sectional study to examine the association of giardiasis with protein-energy malnutrition, vitamin A deficiency and iron deficiency anaemia was conducted among Orang Asli children in Selangor, Malaysia. A total of 281 children aged 2–15 years were studied. The data were collected using structured questionnaires, anthropometric measurements and laboratory analysis of blood and faecal samples. The results showed that 24.9% of the children were infected with Giardia duodenalis, while 56.5, 61.3 and 15.1% had significant underweight, stunting and wasting, respectively. Giardiasis was statistically identified as a strong predictor of significant wasting in this study population.