The objective of the study was to assess the changes that occur in various hematological parameters that may occur in renal failure patients after hemo and peritoneal dialysis sessions. The study was carried out at the AI Neelain University, Khartoum, Sudan. Blood samples were collected from 180 renal failure patients undergoing hemo and peritoneal dialysis (90 each) before and after dialysis sessions. The samples were tested for complete blood count, prothrombin time and activated partial thromboplastin time by the manual calibrated techniques. The study demonstrated an increase of hemoglobin, hematocrit and red cell count after both hemo and peritoneal dialysis. The mean corpuscular hemoglobin and hemoglobin concentration showed mild increase after peritoneal dialysis and slight decrease after hemodialysis. Leukocyte and platelet counts also showed mild increase after hemodialysis, while the prothrombin and activated partial thromboplastin times were significantly prolonged. Our study shows that most of the hematological parameters as well as prothrombin and partial thromboplastin times increased after a dialysis session. Therefore, it is recommended that all patients be screened appropriately before and after dialysis to avoid complications.