This study was carried out to investigate the effect of lavender (Lavandula angustifolia) essential oil addition to broiler diets at different levels on performance, carcass, and blood parameters. A 6-week experiment, 300 unsexed day-old broiler chicks (Ross 308) was used. Six treatments consisting of different lavender essential oil levels (0, 50, 100, 150, 200, and 250 mg/kg) were used with five replicates of fifty chicks per treatment. Body weight (BW), body weight gain (BWG), and feed conversion ratio (FCR) were linearly affected, and these parameters were improved by the addition of lavender essential oil to the diet (P<0.05). However, feed intake was not affected by the supplementation of lavender essential oil (P>0.05). The effect of lavender essential oil on carcass properties was insignificant (P>0.05). The addition of lavender essential oil to the diet linearly decreased LDL, triglyceride, and albumin levels of serum, whereas total protein level of serum linearly increased in broilers. As a result, it can be said that the addition of 250 mg/kg of lavender essential oil to the diet is beneficial in improving the performance and serum parameters of broilers.