The study was carried out to determine the effects of two fructans, long chain inulin and short chain oligofructose, on performance and caecal fermentation in turkeys. Feeding turkeys for 8 weeks with diets containing 2% fructans had no effect on performance indices. Oligofructose significantly lowered ileal pH in comparison with inulin and the control group (5.23 vs 5.90 and 6.04). Both fructans increased the caecal ammonia concentration and lowered caecal pH. Oligofructose increased the production of total short-chain fatty acids (400.8 vs 333.9 and 284.8 μmol/kg BW), especially butyrate (124.8 vs 106.1 and 68.3 μmol/kg BW), in the caeca in comparison with inulin and the control group. Compared with inulin, oligofructose, a fructan with a lower degree of polymerization, more intensively affected the caecal metabolism of turkeys.