The aim of this study is to evaluate the serological levels of zinc, copper and iron in Giardia lamblia-infected children and to study the effect of giardiasis on their weight compared to controls. We studied 30 children, 1-10 years old, who attended the outpatient clinics of Cairo University Pediatric Hospital, with gastrointestinal complaints and diagnosed as having giardiasis by stools examination, they were enrolled as a study group. The control group consisted of 30 age- and sex-matched healthy children, free of gastrointestinal complaints and free of giardiasis. Serological levels of zinc, copper, and iron were measured by atomic absorption spectrophotometer. The infected group had significantly lower weight, serum iron, and zinc than controls (P = 0.035, <0.001, and <0.001 respectively) and 63.3% of patients infected with giardiasis were 1-5 years old. In the infected cases, 60% suffered from of abdominal pain, 50% from weight loss, and 40% had intermittent diarrhea. Infected cases with weight percentiles below the fifth had significantly lower serum iron than those with normal percentiles (>5th). In conclusion, most giardiasis-infected children were between 1 and 5 years, with significant affection of weight, abdominal pain, and/or intermittent diarrhea. Serum zinc and iron levels were significantly decreased in the infected group compared to control (P < 0.001).