Background: The severity of Sickle Cell Anaemia severity varies in different individuals and populations. Some individuals have very mild disease while others have severe disease. The co-inheritance of alpha thalassaemia and sickle cell anaemia provides an interesting example of how separate globin gene mutations can influence the clinical manifestations of an abnormal gene. It was therefore important for the specific clinical effects of alpha thalassaemia in sickle cell anaemia to be determined in Abuja, Nigeria. Aims and Objectives: The aim of the study was to determine the effects of alpha thalassaemia on the haematological and clinical status of patients with sickle cell anaemia at the National Hospital Abuja Methods: Fifty one Sickle Cell anaemia patients who were recruited from 24th January 2013 to 25th April 2013 were enrolled in a cross-sectional observational study. The diagnosis of both haemoglobinopathies were made using PCR. Demographic, clinical and biochemical data were collected using each patient’s case note. Sickle Cell anaemia Severity score was calculated using the Bayesian Network