The use of antibiotic growth promoters in broiler production has been the norm in developing countries, however, the increased rate of antibiotic resistance in humans has resulted in the search for alternatives without negative residual effects. This study investigated the effect of dietary olive garlic extract oil (OGEO) supplementation on the performance and haematological indices of broilers. The experiment lasted for 42 days and broilers were fed varying levels of OGEO‑supplemented diets at the starter (0–21 days) and finisher (22–42 days) phases using two hundred and forty unsexed Ross broilers. Four experimental diets were formulated for the two phases and the diets were designated as diet 1(control (without OGEO)) while diets 2, 3, and 4 were supplemented with OGEO at 1 % (10 g/kg diet) 3 % (30 g/kg diet) and 5 % (50 g/kg diet). Each had four replicates containing fifteen birds per replicate. Performance was measured weekly and haematological indices were determined on days 21 and 42. Data collected were analysed in a one‑way analysis of variance (SAS, 2000) and significant differences were determined using Tukey’s test. Body weight (BW) increased linearly (L) (