Abstract: The toxicological effects of Tithonia diversifolia Gray was evaluated in albino rats using crude aqueous extract administered oraly for 14 days. Changes observed in haematological parameters, serum biochemical parameters and histopathological reports were used as indices for toxicosis. The aqueous extract of T. diversifolia caused statistically significant (p< 0.05) reductions in Packed Cell Volume (PCV), Total Red Blood Cell count (TRBC) and Haemoglobin (Hb) levels at the 200 mg kg ¹ b.w. treatment group. It also caused a statistically significant (p< 0.05) increase in MCV and MCHC values in both 100 and 200 mg kg ¹ b.w. treatment groups. This suggest that this plant may cause macrocytic hyperchromic anaemia in animals consuming them. The serum biochemistry revealed that the aqueous crude extract of T. diversifolia at the dosage of 100 and 200 mg kg ¹ b.w. caused a statistically significant (p< 0.05), increase in Alkaline Phosphatase (ALP), Alanine amino Transferase (ALT) and Aspartate amino Transferase (AST) levels. This may be indicative of hepatocellular damage which is further confirmed by a statistically significant (p< 0.05) increase in the Total Bilirubin (TB), reflected in the histopathologic lesions of multifocal vacuolar degeneration, necrosis and thinning of the hepatic cord in the centrolobular region. The marked congestion of the renal capillaries with diffuse degeneration and necrosis of the tubular epithelium, also with focal area of perivascular lympocytic infiltration observed in the histopathology of the kidney can be explained with the statistically significant (p< 0.05) increase observed in the values of Total Protein (TP) and Albumin (ALB).