A study was conducted to determine the effects of feeding γ-aminobutyric acid (GABA) and hydrochloric acid (HCl) on the growth performance, nutrient digestibility and fecal score in growing pigs. Ninety Duroc × (Landrace × Large Yorkshire) growing pigs with an average initial body weight (BW) of 25.51 ± 1.63 kg were randomly allotted to three treatment groups with 6 replications of 5 pigs per replicate pen for each treatment in a 6-week trial period. The treatments were as follows: 1) basal diet (CON); 2) basal diet with 0.05% GABA and 3) basal diet with 1% of a 10% HCl solution. The results showed that GABA supplementation significantly increased the average daily gain (ADG) (p < 0.05) compared with the control during week 4 and the overall experiment period (0 to 6 weeks). However, HCl supplementation had a numerical increase in the ADG compared with the control. The total tract digestibility of dry matter (DM) was greater in GABA group than the CON (p < 0.05). The supplementation of GABA and HCl in the diet of growing pigs had no significant effect on the fecal scores compared with the CON. Experimental results show that supplementation of 0.05% GABA in the diet of growing pigs had a positive effect on the ADG and DM digestibility in growing pigs.