The objective of the present experiment was to investigate the influence of dietary CP, standardized ileal digestible ( SID) Lys level and their interaction in male Ross 308 broilers. From day 10, six experimental treatments were tested until day 35. The six experimental treatments consisted in a 3 × 2 factorial design with 3 levels of dietary SID Lys/CP (equaivalent to 3 levels of dietary CP) and 2 levels of dietary SID Lys. Growth performance, uniformity, carcass traits, litter quality, blood & gut parameters, nitrogen ( N ) emissions and global warming potential ( GWP ) were measured or calculated. There was no interaction for all criteria except for NH 3 and N 2 O volatilization. The increase of dietary SID Lys/CP did not affect growth performance or uniformity, increased abdominal fat yield, decreased all N related parameters (litter N, blood uric acid, N excretion, NH 3 and N 2 0 volatilization). There was an interaction between dietary CP and AA origin for GWP; GWP was further reduced after CP reduction when using AA from EU. Increasing SID Lys improved growth performance, increased uniformity, increased breast meat yield, reduced abdominal fat yield, but increased N emissions and GWP. This study indicates that dietary CP can be drastically reduced in different nutritional contexts without negatively affecting growth performance, and with positive benefits on the environment.