Abstract The effect of the administration of methanolic extract of root of Guiera senegalensis on some biochemical and hematological parameters in Wister strain albino rats was investigated. After a period of about 28 days the rats given methanolic root extract of Guiera senegalensis showed no significant increase or decrease in the levels of the biochemical parameters compared to the rats receiving 2 ml of distilled water. That is the extract did not alter the levels of Aspartate transaminase (AST) Alanine transminase (ALT), alkaline phosphatase (ALP), Total protein and albumin. Also the levels of Urea, Creatinine, sodium, potassium, chloride and bicarbonate were not altered. There was no statistically significant change in the mean values of the hematological parameters, when compared with those of the control group.