Two experiments were conducted to compare the effects of different organic acids on growth performance and apparent nutrients digestibility in weaned pigs. In both the experiments, 180 pigs were assigned to four treatments with three replicates comprising of 15 pigs in each. Formic acid, ammonium-formate, lactic acid, and acid mixture were added to diets at 0.50% (Exp. 1) and 0.30% (Exp. 2) as dietary treatments for 5 and 6 wk feeding trial, respectively. The acid mixture was prepared by mixing formic acid and lactic acid at 50:50 ratios. To investigate the apparent ileal amino acids digestibility, twelve pigs (3 per treatment) were used and fitted with simple ileo-caecal T-cannula for both experiments. In Exp.1, growth performance was comparable (P>0.05) among pigs fed different organic acids, while acid mixture had higher (P<0.05) weight gain than that of lactic acid in Exp.2. The apparent ileal digestibility of amino acids was highest (P<0.05) in pigs fed acid mixture and lowest (P<0.05) in pigs fed formic acid diets in both experiments. These results indicated that supplementation with acid mixture (formic acid and lactic acid) improved performance and ileal amino acid digestibility in weaned pigs.