Abstract: The biochemical and haematological indices of birds fed with varying dietary inclusions of siam weed (Chromolaena odorata) leaf meal (SWLM) were determined using 24 laying hens in their eighth month of lay in an eight week trial. Four diets were formulated for the purpose of this study. Diet 1 served as the control diet and had no SWLM inclusion. SWLM was introduced at 2.5%, 5.0% and 7.5% in diets 2, 3 and 4 respectively. The haematological and biochemical investigations revealed no statistical differences (P=0.05) among the mean values of treatments 1, 2 and 3. However the mean value of treatment 4 (7.5% SWLM inclusion level) was statistically different (P<0.05) from the others. The numerical values of most haematological indices showed an initial increase up to treatment 3 followed by a decrease in treatment 4. Almost all haematological indices studied (PCV, RBC count, Hbc, MCHC, MCH, MCV and ESR) progressively increased up to diet 3 (5% SWLM inclusion) after which there was a decline indicating a probable acceptance limit of 5% SWLM dietary inclusion in layers diets without any serious health implication.