A study was conducted to understand effects of feeding soy NSP exogenously added in typical starter diet in broiler chicks on performance, GI microbiota, nutrient digestibility and dietary net energy availability. Initially, the bulk extraction of Cell Wall Material (CWM) (non-starch polysaccharide levels (NSP) analyzed value~ 27% on DM basis) and soluble non- cellulosic polysaccharides (NCP) from SBM were performed to conduct in-vivo study. Two treatment diets were created: T1-common starter (Cobb 500 nutrient specs); and T2- starter +CWM (at 3 %) + 0.2 %, soluble NCP (via drinking water). Birds (Cobb 500) were reared using floor pens (n= 40 birds/treatment) until d 6 with common starter diet. Broiler chicks were then fed experimental diets from d 7 to d 14. Performance was measured at d 12. GI microbiota was assessed using 16s rRNA gene sequencing for ileal and cecal digesta before (d 6) and after feeding treatment diets (d 12). NCP and amino acid (AA) ileal digestibility were measured using TiO2as indigestible marker in feed and ileal digesta. Dietary net energy (NE)were measured calculating heat increment HI (Fed heat production (HP) – Fasted HP) and subtracting it from metabolizable energy. Results showed that BW recorded on d12 were 342 g/b and 302 g/b whereas FCR was 0.96 and 1.1 respectively for T1 and T2 groups. T2 had a lower digestibility coefficient (P < 0.05) for all the AA analyzed (by 3-5 units). Total NCP digestibility was higher for T1 diet (by 7 units). Microbiota results showed ileal Lactobacillus acidpiscis went to higher abundance for TI and T2 from d 6 to d 14. Unclassified Lactobacillus and E. coli were higher in T2 (P<0.05). In cecal digesta, E. coli abundance went up (P<0.05) for T2, whereas Enterococcus abundance were higher in T1. Even though there were difference in body composition (BC) (protein: fat ratio was higher for T1 at d 12 and d 14), significant difference in HI was not observed between treatment groups, thus not differing in the dietary net energy (Kcal/ kg of FI) value between treatment diets.