This study was conducted to evaluate the effects of providing fermented soy protein to weaned pigs on nitrogen balance and apparent fecal and apparent ileal digestibility (AID) of AA. Four weaned ((Yorkshire${\times}$Landrace)${\times}$Duroc) barrows (BW = 6.58${\pm}$0.98 kg), surgically fitted with a simple T-cannula approximately 15 cm prior to the ileo-cecal junction, were fed four diets according to 4${\times}$4 Latin square design. Diets were a basal diet supplemented with one of the following: 3% SDPP (spray dried plasma protein), 5% RBP (soy protein fermented by Lactobacillus spp.), 5% PSP (soy protein fermented by Aspergillus oryzae and Bacillus subtilis), and 2.5% RPP (2.5% RBP+2.5% PSP). No differences were observed in DM and N intakes among treatments. However, the level of urine excretion was greater in the RPP group than in the PSP group. Additionally, fecal DM excretion, fecal N concentration and fecal N excretion were increased in the RBP, PSP and RPP groups when compared with the SDPP group (p<0.05). Furthermore, total excretion was increased in the RPP group when compared with the PSP group (p<0.05). In addition, N absorption and the N absorption ratio were higher in the SDPP group than in the RPP group (p<0.05). Moreover, the DM and N digestibilities were lower in the RBP, PSP and RPP groups than in the SDPP group (p<0.05), and the ash and energy digestibilities were higher in the SDPP and RBP groups than in the PSP and RPP groups (p<0.05). However, no significant differences were observed in the DM, N, Ash, Ca, P or ileal digestibilities among treatments, although the energy digestibility was higher in the SDPP group than the RBP group (p<0.05). In addition, the apparent ileal digestibilities of essential amino acids (Arg, His, Iso, Leu, Lys, Phe, Thr, and Val) were significantly higher in the SDPP group than in the other groups (p<0.05), and the levels of Ala, Cys, Glu and Try were greater in the SDPP treatment group than the RBP, PSP and RPP groups (p<0.05). Additionally, the levels of Asp, Gly and Ser were higher in the SDPP group than the PSP and RPP groups, and the level of Pro was higher in the SDPP group than the RPP group (p<0.05). Finally, total non-essential amino acid and total amino acid digestibility were higher in the SDPP group than in the other treatments (p<0.05). Taken together, the results of this study indicate that animal protein is more bioavailable than plant protein. However, the N absorption ratio and ileal digestibility were found to be similar in the SDPP and RBP groups.