Bidens pilosa is used empirically for the treatment of various illnesses among which are: jaundice, conjunctivitis, cataract, malaria, ulcers and hypertension. This study is aimed at evaluating the subchronic toxicity of the leaf aqueous extracts of B. pilosa. The effects of the administration of the aqueous extracts of B. pilosa on physical (body weight, relative weight of organs), biochemical and histological parameters were studied in male and female albino Wistar rats. Daily doses of extract (100, 500 and 1000 mg/kg) and distilled water were administered orally for 4 weeks; during which signs of toxicity were checked. At the end of the experiments, the rats were sacrificed, their blood and organs collected for biochemical, histological and haematological analyses. No death was recorded. At the end of the treatment, there were no significant (P>0.05) variations of the body weight gain and the relative weights of detoxification organs (liver and kidney). The analysis of biochemical parameters showed a significant (p<0.001) variation of serum levels of ALT and creatinin. Histological analysis of liver and kidney, revealed no modification. The analysis of haematological parameters showed no significant difference between males and females, overall. However, when considering each sex in particular, it was observed that in males red blood cell distribution width-coefficient variation (RDWcv) significantly increased at the doses of 500 mg/kg (P=0.02) and 1000 mg/kg (P=0.04) (vs. control). Unlike in males, white blood cells (WBC) in females decreased significantly at 500 (P=0.01) and 1000 mg/kg (P=0.01) (vs. control). It can be concluded that Bidenspilosa has a relatively low toxic effects in both sexes, with some gender differences in the haematological results.