Background: Sickle cell disease is a protean disease with limited data on the phenotypic and genetic variants in Nigeria. This study was conducted to provide baseline data on these variants by characterizing the existing forms of sickle cell disease and correlating these with basic hematological parameters. Methods: Adult and pediatric patients with SCD were recruited from a tertiary health centre in Nigeria. Patients were age and sex matched with healthy controls. Blood samples were obtained for Full Blood Count, phenotyping by High Performance Liquid Chromatography and genotyping for alpha thalassemia by multiplex gap polymerase chain reaction. Data analysis was done using IBM SPSS statistics version 23. Results: A total of 130 patients with sickle cell disease and 117 controls were studied. Alpha thalassemia in the study population was due to a 3.7kb deletion in the alpha globin gene cluster at a prevalence of 45.4% in the patients and 47% in controls. The prevalence of the various existing forms of SCD genotype was: Homozygous S without alpha gene deletion (HbSS)- 39.2%; HbSC - 10.8%; HbSα+1- 35.4%; HbSα+2 - 6.9% and HbSF- 7.7%. HbA2 was significantly elevated in individuals with two alpha gene deletions (HbSα+2). HbF and HbA2 were negatively correlated with each other (r= -0.587, p < 0.001). Individuals with the HbSC genotype followed by HbSα+2 had the best hematological parameters. Conclusions: Hematological parameters varied with hemoglobin genotype. The C hemoglobin and homozygous alpha thalassemia deletion had better ameliorating effect on SCD hematological parameters than the F hemoglobin in this population.