This study aimed to investigate the effects of pre-incubation in ovo injection with different levels of L- carnitine (L-Car) on hatchability traits of Bronze Turkey eggs, blood plasma constituents and subsequent growth performance of hatched chicks. A total of 300 hatching eggs of Bronze Turkey were chosen (averaged 80.0 g) and randomly divided into four main groups each of three replicates (25 eggs each). The 1^st group was used as a control (C) without injection, while the 2^nd, 3^rd and 4^th groups were injected with 0.1 ml distilled water contained 6, 8 or 10 mg L-Car/egg, respectively. Hatchability (%), Early and late embryonic mortality (%) were calculated. After hatch, 33 chicks were taken from each treatment group then distributed into three replicates (11 chicks, each), then reared up to 84 d-old to evaluate their growth performance. The results indicated that, in- ovo L-car injection (with 6.0 mg/egg) before incubation had significantly (P≤0.01) increased hatchability (%) of fertile eggs and decreased (P≤0.01) both early and late embryonic mortality compared with the control group (non-injected). Hatched chicks from injected eggs with 6.0 mg L-car /egg recoded a significant (P≤0.01) improvement of all studied growth traits during the entire period after hatch as compared with the other treatment groups.  Blood PlasmaIGF-1, triiodothyronine and total antioxidant capacity constituents were significantly elevated for chicks at hatch by in ovo L-car injection compared to control group. Histological examination explained an improvement in small intestine and lymphoid organs development by in ovo L-car injection compared to the control group.  So, we concluded the in ovo L-car injection (6 mg/egg) before incubation could be used as a promising technical method to improve hatchability and decrease embryonic mortality (%), obtain better immunity and subsequent growth performance of Bronze turkey chicks after hatch.