Background: There are scant evidences between giardiasis and enterobiasis with human mal-absorption of micronutrient. Objectives: The aim of the present study was to found out the changes in the serum zinc, copper, magnesium and vitamin B12 levels in schoolchildren infected with Giardia intestinalis and Enterobius vermicularis. Patients and Methods: This case-control study was carried out among 359 children from aged 6 -12 years old at 8 suburban public schools. Three stool examinations were done using standard techniques for identification parasitic infection. Fifty E. vermicularis and 37 G. lamblia infected individuals were enrolled as study groups. Serum levels of copper, zinc, magnesium were assessed by autoanalyzer and vitamin B12 levels were measured using gamma counter. ANOVA and paired t-test analyses were used to determine the association between infections and trace elements changes. Results: The prevalence of G. intestinalis and E. vermicularis infections were 10.3% and 13.9%, respectively. The serum zinc, copper and magnesium levels showed a significant decrease in individuals infected with G. intestinalis and E. vermicularis (P < 0.05). Mean values of Giardia positive and negative groups for copper 143.65 ± 16.51 and 176.26 ± 17.6 μg/dL, zinc 62.26 ± 16.06 and 80.66 ± 23.58 μg/dL, and magnesium 1.82 ± 0.23 and 2.01 ± 0.16 mg/dL, respectively. Mean values of Enterobius positive and negative groups for copper 145.55 ± 26.84 and 176.26 ± 17.6 μg/dL, zinc 72.7 ± 17.92 and 80.66 ± 23.58 μg/dL and magnesium 1.93 ± 0.11 and 2.01 ± 0.16 mg/dL, respectively. Conclusions:The results showed that giardiasis and enterobiasis decreased serum levels of copper, zinc and magnesium. Further studies are needed to clarify the actual mechanism governing the zinc, copper, magnesium and vitamin B12 giardiasis/enterobiasis interaction.