This aim of the study was to evaluate the effect of Achyranthes japonica Nakai extract (AJE) supplementation to a low-protein diet on growth performance, nutrient digestibility, excreta bacterial count and excreta gas emission in broilers. In total, 600 one-day-old male Ross 308 broilers, with an average body weight of 42.90 ± 1.43 g, were randomly divided into 20 birds/pen. In a 2 × 3 factorial design, pens were assigned to one of six dietary groups: highcrude protein (HCP) vs low-crude protein (LCP) supplemented with 2 doses (0.025%, 0.050%) of AJE or without supplementation (0%). The experimental diets were fed to broilers from day 8 to 35. The HCP diet resulted in higher body weight gain (BWG) and lower feed conversion ratio (FCR) compared to the LCP diet in all phases of the experiment. AJE (0.05%) supplementation increased BWG from day 22 to 35 and in the entire period of LCP diet administration. AJE supplementation to the LCP diet caused lower FCR between days 22 and 35, and an overall higher feed intake (FI). AJE showed a linear increase in BWG, FI and nitrogen digestibility over the entire trial period. Increasing doses of AJE linearly reduced the Escherichia coli count in excreta, and 0.05% AJE supplementation in the LCP group resulted in the lowest E. coli count. NH3 emission was reduced in the group supplemented with 0.05% AJE. No interaction effect of CP and AJE was observed. When added to a low-protein diet, AJE supplementation presented a promising ability to sustain similar growth performance by improving nitrogen digestibility and modulating the intestinal bacterial population in broilers.