Sickle cell anemia (SCA) is one of the inherited hemoglobin disorders with substantial morbidity and early mortality. Hydroxyurea is the US Food and Drug Administration (FDA)-approved medication that has emerged as the primary disease-modifying therapy for SCA. Our purpose is to summarize the available evidence regarding the pharmacology, clinical efficacy, and safety of hydroxyurea therapy for the treatment of SCA. The electronic databases PubMed and Embase were searched from their starting dates to May 31, 2016. Databases were searched using the following terms: sickle cell, hydroxyurea, nitric oxide, dosing, therapeutic, and safety monitoring. Hydroxyurea therapy may cause severe myelosuppression when used in patients with SCA. SCA patients are initially treated with hydroxyurea at 10 or 20 mg/kg, and then the dose- is escalated to mild myelosuppression using a standardized regimen. Routine blood monitoring should be performed while the patient receives hydroxyurea treatment. Hydroxyurea can increase fetal hemoglobin (HbF) level and ameliorate some of the vascular symptoms in patients with SCA. Hydroxyurea therapy may help to avoid frequent hospitalizations, especially in patients with vaso-occlusive crisis. Taken together, available evidence suggests that hydroxyurea represents an inexpensive and effective treatment option that should be offered to patients with SCA.