Protected organic acids are suggested to more effectively deliver acids to the distal ileum, cecum, and colon of piglets. The objective of this study was to evaluate the effects of dietary supplementation of protected organic acid blends (17% fumaric acid, 13% citric acid, 10% malic acid, 1.2% medium chain fatty acid) and carrier on growth performance, nutrient digestibility and fecal micro flora in growing pigs. A total of 100 crossed [(Landrace × Yorkshire) × Duroc] with an average initial BW of 23.4 kg was used in a 6-wk trial. Pigs were randomly allocated into 1 of 4 treatments (5 replications with 5 pigs per pen) in a randomized complete block design based on their BW. Treatments consisted of a control diet (CON) and the control plus 0.1, 0.2, and 0.4% of organic acid blends. Body weight and feed intake were measured initially and at the end of 6 wk to determine average daily gain (ADG), average daily feed intake (ADFI) and gain/feed. The digestibility of nutrients and fecal micro flora was also assessed at the end of the experiment. Data were analyzed using contrast statements to test the linear and quadratic effect of organic acid concentration in the diet. Linear effects (P < 0.05) were observed for ADG (713 g, 724 g, 745 g, and 737g) as well as G:F (0.450, 0.456, 0.471, and 0.464) with the increase in the level of organic acid blends. Dietary supplementation with 0.1%, 0.2% and 0.4% protected organic acid did not affect DM, N and energy digestibility. Supplementation of organic acid blends in the diet linearly increased (P < 0.01) fecal Lactobacillus population counts (7.26, 7.31, 7.47, and 7.38 log ₁₀ cfu/g) with the increase in the dose of organic acid blends. Our result suggests that protected organic acid has the potential to enhance growth performance and improve microbial population in growing pigs.