Generally, most of the hematological and biochemical parameters in SCD patients are different from that of the other population. Hence, the importance of laboratory reference values for SCD has received a wide attention lately. However, there is a few reliable data to serve as reference values for hematological and biochemical parameters in patients with SCD in most African countries [3]. This study aimed at determining the hematological parameters in adults with sickle cell disease visiting the University College Hospital, Ibadan, Nigeria, with a view to providing a predictive data of SCD patients hematological parameters, as well as contributes to effective management of the disease. 131 participants were studied, 95 were sickle celled while 36 were healthy controls. Plasma was separated from collected blood and used to determine the haematological parameters. Results showed that the mean age was 35.4years ±SD=7.54years with a range of 19 to 56years for sickle cell subjects and 36.8years ±SD=9.11years with a range of 19 to 58years for control. The male to female ratio was approximately 2:1 and 2.4:1 in control and sickle cell subjects respectively. All respondents (100.0%) had abnormal haemoglobin, (78.9%) had abnormal leucocytes and 21.1% had abnormal platelets. Student’s t-test revealed that there was no significant relationship between the haematological parameters assessed in the HBSS patients (Haemogloblin vs Leucocytes, 093(.369), Haemogloblin vs platelets, 031(.767), Leucocytes vs platelets, .023(.825). It is therefore advisable to always check for each parameter and never use one to predict the other, for effective management of sickle cell disease.