Giardia is a major causative agent of gastrointestinal disease in humans and causes giardiasis. The present study utilised microscopy and ELISA copro-antigen to determine the prevalence of Giardia lamblia in stool samples of children 0-5years presenting with gastroenteritis in association with body mass indices (BMI) in Kaduna Metropolis, Nigeria. Of 200 samples examined, 12 (6%) were positive for Giardia lamblia using microscopy and 28 (14%) using ELISA kit. The prevalence of giardiasis was higher in males (15.89%) than females (11.83%). There was no significant difference in the level of infection in both sexes (χ2=0.6811, df= 1, p < /em>= 0.4092). The highest prevalence of giardiasis was observed in 4-5 years (16.39%) while the lowest was in the 0-1 year (9.68%). There was no significant difference in the prevalence of giardiasis among the age groups (χ2= 0.848, df= 4, p = 0.9319). There was no association between giardiasis and BMI (p = 0.3161). The study showed that 33% of the children were underweight, while 66% and 1% had normal weight and overweight respectively. There was a strong association between giardiasis and source of drinking water (well water), nutritional status, and mother's level of education. The most common parasite identified in this study was Entamoeba coli (18%) followed by Giardia lamblia (14%) and the least was Strongyloides stercoralis (0.5%). Based on the above results, it can be concluded that the prevalence of Giardia lamblia in children 0-5 years presenting with gastroenteritis has no association with their BMI. Therefore it is important that children 0-5 years should be fed with a balanced meal. Improved personal hygiene should be encouraged and treated water should be protected from re-contamination.