Two experiments were conducted to determine the influence of sources or concentrations of dietary fiber in nitrogen-free diets (NFD) on basal ileal endogenous losses (BEL) of amino acids (AA) and subsequent standardized ileal digestibility (SID) of AA in feed ingredients for pigs derived from such BEL. In Exp. 1, 20 pigs (initial body weight = 46.5 ± 2.97 kg) were assigned to five diets in a quadruplicate 5 × 2 incomplete Latin square design with two periods. Three NFD containing cellulose (insoluble and fermentable fiber), inulin (soluble and fermentable fiber), or carboxymethyl cellulose (CMC; soluble and non-fermentable fiber) at 40 g/kg plus two diets containing soybean meal (SBM) or wheat distillers’ dried grains (WDDG) as the sole source of nitrogen were prepared. Pigs fed NFD containing CMC had greater (P < 0.05) BEL of AA, except for Arg and Pro, than those fed the other NFD. The SID of most AA in SBM and WDDG corrected by BEL of AA from NFD containing CMC were greater (P < 0.05) than those corrected by BEL of AA from the other NFD. Experiment 2 was conducted with 21 barrows (initial body weight = 34.1 ± 2.57 kg) assigned to seven diets in a triplicate 7 × 3 incomplete Latin square design with 3 periods. Seven diets consisted of three NFD containing 4, 8, or 12 g/kg cellulose and four diets containing corn, wheat, SBM, or canola meal as the sole source of nitrogen. There was no difference in the BEL of AA, except for Pro, among pigs fed NFD with increasing concentration of cellulose. The SID of AA in test ingredients were not affected by BEL of AA from NFD containing increasing concentration of cellulose.