Metallic nanoparticles serve as vehicles for delivery of bioactive molecules from plants having distinct advantages over crude extract, which includes enhanced solubility, bioavailability and pharmacological activity. Annona muricata leaf aqueous extract acted as the reducing and stabilizing agents with aurochlorohydric acid as the substrate. In the characterization studies of the biofunctionalized gold nanoparticles (A*AuNP), UV-Vis spectroscopy was used to determine the surface plasma resonance vibration, X Ray Diffractometry was used to determine the structure and FT-IR spectroscopy was used to determine the functional groups present. Male Wister rats were administered doses of 100 or 200mg A*AuNPs/kg body weight and also 100mg/kg body weight of crude extract, AMAE and gold nanoparticles standard, S*AuNPs. The effects of the treatments on hematological parameters were determined in the plasma using standard techniques. Erythrocyte osmotic fragility was determined spectrophotometrically. The reduction of gold ions into gold nanoparticles (i.e. Au3+ to Au0) took place within 45 min of reaction time at 60oC and pH of 9.2. The characterization studies reported that the average crystalline size of the formed nanoparticles was 13nm. The study suggests that A*AuNPs exhibited significant changes (P<0.05) in some hematological parameters in rat model and significant reduction (P<0.05) in erythrocyte osmotic fragility compared to control group and therefore offers potential to be exploited for various biotechnological use.