The aim of this study was to determine the effects of xylanase and flaxseed the performance of chickens, digesta viscosity, nutrient retention, fatty acid profile in muscle, tibia strength and interrelations of these factors in broiler chickens fed a wheat-based diet. Seven hundred and twenty one-day-old Ross 308 cockerels were assigned to four treatments according to the contents of flaxseed (0 and 80 g/kg) and xylanase (0 and 0.1 g/kg) in the diet. Xylanase significantly decreased the intake of feed (p < 0.001), decreased feed conversion (p < 0.001), and reduced mortality (p = 0.050). In addition, xylanase significantly increased the retention of all nutrients (p = 0.010 -