Background: Bone marrow suppression as a serious complication of chemotherapy induces leucopenia or neutropenia that results to hospitalization and antibiotic therapy. Several studies used zinc supplement for reduction of chemotherapy side effects’, these studies showed that zinc can prevent metastasis, local recurrence and increases survival rate, so this study conducted to evaluate preventive effect of oral zinc sulphate on hematologic changes induced by chemotherapy. Material and Methods: This double blind randomized controlled trial enrolled 50 adult patients who were under chemotherapy during 2008-2009. Subjects were randomly divided into two groups. By the beginning of chemotherapy, the patients in each group received three 220 mg zinc sulphate capsules daily (Alhavi Co.) or placebo capsules provided by zinc sulphate manufacturing company, which were similar in shape, taste and color to zinc sulphate capsules. This diet followed up to end of study. Then data was analyzed by SPSS17 software using independent sample T-test. Results: There was no statistically significance between white blood cell count (p=0.7), red blood cells count (p=0.4) and hemoglobin (p=0.9) in zinc sulphate and placebo groups (CI=95%). Conclusion: It can be concluded that zinc sulphate cannot prevent hematologic changes induced by chemotherapy.