The present experiment was conducted to investigate the effect of a different dietary content of sunflower meal (SFM) and the efficiency of an non-starch polysaccharide (NSP)-degrading enzyme preparation on growth and gut function of young turkeys. A total of 1512 one-day-old male turkey poults were randomly assigned to 8 dietary treatments, with 7 pens per treatment and 27 birds per pen. Experimental diets with a different content of SFM (0, 7, 14 and 21%; SFM₀, SFM₇, SFM₁₄ and SFM₂₁ groups, respectively) were administered in two variants, with and without NSP-degrading enzymes (E+ and E₀ treatments, respectively). Diets fed to the turkeys for 8 weeks were isonitrogenous and isocaloric, but they differed substantially with regard to crude fibre content (in average 2.98, 3.97, 4.64 and 5.64% in the SFM₀, SFM₇, SFM₁₄, and SFM₂₁ groups, respectively). The enzyme preparation applied to a diet caused a tendency towards lower ileal viscosity (P=0.099) and a significant decrease in caecal total volatile fatty acids concentration, despite of the observed increase in activities of bacterial α-glucosidase, α-galactosidase and β-galactosidase in the E+treatment. At the same time, two-way ANOVA revealed that following the dietary inclusion of SFM at the amount of 14 and 21%, a significant decrease was observed in final body weight, small intestine and caecal tissue mass, caecal digesta mass, as well as the rate of bacterial production of volatile fatty acids in the caeca. Such an effect was not recorded when SFM was applied at a dose of 7%. In conclusion, sunflower meal rich in crude fibre added at the level of 14-21% to a diet for growing turkeys may induce undesirable processes manifested in the decrease in relative mass of small intestine and caecal tissues, as well as potent inhibition of the fermentation processes in the caeca. Our study showed additionally that high fibre sunflower meal could be used at a dose of up to 7% without any adverse effects on the gastrointestinal physiology of the growing turkeys.