The effects of in ovo amino acid administration on hatchability traits and post-hatch performance were studied using eggs from a meat-type breeder flock (Ross) at 38 weeks of age. On day 15 of incubation, five treatments were applied, consisting of six replicates with 16 eggs per replicate. The treatments consisted of a non-injected negative control; a positive control in which saline was injected; and three treatments with saline, containing 23.72 mg lysine, glutamine, glycine and proline (AA1); 23.60 mg arginine, glutamine, glycine and proline (AA2); and 28.76 mg lysine, arginine, glutamine, glycine and proline (AA3). The hatchability traits were incubation period, chick weight at hatch as an absolute value (CWT) and chick weight at hatch as a percentage of egg weight (CWTP), and the post-hatch performance traits were body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR). Measurements on the chickens were taken during the starter (1 – 21 days of age), finisher (22 – 35 days of age) and entire (1 – 35 days of age) experimental periods. In ovo amino acid treatments improved CWTP without affecting hatchability traits, and increased FI without altering the FCR of chickens during the entire experimental period. Chickens of the in ovo AA1 treatment had a higher FI than those of the control treatments during the finisher period. In ovo AA2 treatment increased CWT and BWG of the chickens during the starter period and entire experimental period and FI during the finisher period, when compared with those of the control treatments. In ovo AA2 treatment resulted in a longer period of incubation than those of other treatments. It was concluded that in ovo amino acid treatment increased CWTP and FI of chickens without affecting hatchability traits and feed efficiency and in ovo of AA2 treatment increased the incubation period, CWT and BWG when compared with those of control treatments during the entire experimental period.