Background: Helicobacter (H.) pylori is the most common chronic bacterial infection of humans; affecting ~50% of the world's population. It is the cause of disease states of varying degrees of severity. Anemia is a widespread public health problem; ~50% of cases are diagnosed as iron deficiency anemia (IDA). Recent studies have suggested an association between H. pylori infection and IDA in children. Aims of the work: this study was conducted to evaluate the prevalence of H. pylori infection in children with and without IDA diagnosis and also to determine effects of the bacterium on complete blood count parameters of those children. Subjects and Methods: a case-control (retrospective) study design was chosen to conduct this research. The prevalence of H. pylori antibody (Ab) seropositivity was compared between 50 children diagnosed with IDA vs. 50 non-anemic control children matching in age and sex. Results: a total of 18 (36%) anemic and 10 (20%) non-anemic children were found positive to H. pylori Ab (P=0.0013). Also, comparison of the anemic to the control group revealed statistically significant lowering of ferritin, and red blood cell (RBC) parameters (i.e., hemoglobin, packed cell volume, mean corpuscular volume, and mean corpuscular hemoglobin), and also platelet count in the anemic group. Moreover, comparison of H. pylori positive and negative anemic children revealed statistically significant lowering of RBC parameters in the H. pylori positive anemic children. Also, comparison of H. pylori positive and negative children revealed statistically significant lowering of RBC parameters in H. pylori positive children. In addition, correlation of H. pylori with all other parameters revealed negative significant correlation between H. pylori and RBC parameters. Conclusions: H. pylori infection had a higher prevalence among preschool children with IDA and the hematological impact was more on H. pylori positive anemic children. Recommendations: both IDA and H. pylori are treatable diseases, so children having IDA must be investigated for H. pylori infection for early treatment to avoid serious complications of both diseases.