Two hundred and fifty six broiler chicks were randomly grouped into eight treatments and were fed diet without (T1) or with supplementation of antibiotic growth promoter (T2), or with supplementations of lemongrass oil at 100 mg/kg diet (T3), 200 mg/kg diet (T4), 300 mg/kg diet (T5) or thyme oil at 100 mg/kg diet (T6), 200 mg/kg diet (T7) and 300 mg/kg diet (T8). The experiment revealed that T1 had significantly lowest body weight and weight gain among all treatment groups. The groups T3, T4, T6 and T8 did not differ significantly with T2, whereas, T7 and T5 had significantly higher body weight gain than T2 and control. No significant difference was observed among treatments groups in cumulative feed intake. At the end of experimental period, the feed conversion ratio of broilers was significantly better in T7 followed by T5 and T8, than T6, T4, T3 and T2, whereas the control (T1) recorded poorest feed conversion ratio. There was no significant difference in livability among treatment groups. The group T8 had significantly higher villi length followed by the groups T7 and T6 than other treatment groups, whereas it was lowest in T2. All the groups fed with the essential oils recorded significantly higher apparent digestibility of protein and retention of calcium and phosphorus than T1 and T2. The groups T5, T4, T3 had significantly lower total cholesterol in serum, breast and thigh muscle than control (T1) and antibiotic supplemented group (T2). Return over feed cost was highest in T7 and it was lowest in control group. The supplementation of antibiotic (T2) increased the return-over-feed cost (ROFC) than control. The groups T3 and T6 produced comparable ROFC with T2, but T4, T5 and T8 produced higher ROFC than T1, but lesser ROFC than T2. Hence, it may be concluded that lemongrass oil up to 100 mg/kg or thyme oil up to 200 mg/kg broiler diet could be supplemented as an alternate to antibiotic growth promoter, without compromising the economics of broiler farm.