The purpose of this study is to investigate the effects of extract of Eugenia uniflora on some haematological parameters of male Wistar rats. A total of 24 male Wistar rats were used in the study. They were divided into four groups of six (6) rats each. Group 1 functioned as the control group and received distilled water while Groups 2, 3 and 4 received 200mg/kg, 400mg/kg and 800mg/kg extract of Eugenia uniflora respectively. The administration was done orally once daily for 30 days. At the end, the rats were sacrificed under light chloroform anaesthesia and their blood collected for analysis of haematological parameters. Data was analysed using SPSS version 23 (SPSS incorporated, Chicago, Illinois, USA). Results are expressed as mean±standard error of mean (SEM). Significant differences were determined by one-way analysis of variance (ANOVA). The differences in values were considered to be statistically significant at p<0.05. The packed cell volume (PCV) decreased significantly in some test groups when compared to control. The RBC count and Hb concentration also decreased significantly. There was a significant increase in white blood cell count amd neutrophils but reductions in lymphocytes and mean corpuscular haemoglobin concentration. Result of the study has shown that the hydromethanolic extract of Eugenia uniflora may possess anti-erythropoietic actions because of the significant reductions in RBC count and Hb concentration as well as leucopoetic and possibly immunomodulatory actions which boosted white blood cell (WBC) production.