Flax seed is a rich source of α-linolenic acid (18:3 n-3). Feeding broiler birds flax seed can increase n-3 fatty acids in meat tissues. However, non-starch polysaccharides in flax seed decrease nutrient digestibility and can have a negative impact on bird performance and muscle fatty acid content. Addition of carbohydrase enzymes to flax-based broiler diets can decrease the anti-nutritive effects of non-starch polysaccharides. An experiment was conducted to investigate on the effect of flax seed and carbohydrase enzyme foregut morphology, muscle tissue, fatty acids, and bird performance. A total of 112 five-day-old broiler chicks were assigned to one of four treatments: Flax10 (corn-soybean meal basal diet adjusted for 10% flax), Flax15 (basal diet adjusted for 15% flax), Flax10E (Flax10 + 0.05% enzyme), and Flax15E (Flax 15 + 0.05% enzyme). Addition of enzyme led to large increases in villi height and villi width in the jejunum of birds fed Flax10 and increases in crypt depth in the jejunum of birds fed Flax15 (P < 0.05). The ratio of villi height to crypt depth was larger in the duodenum and jejunum of birds fed Flax10E when compared to Flax10 (P < 0.05). Feeding the Flax15 diet led to a significant decrease in total lipids in breast muscle compared to Flax10 (P < 0.05). The effect of level of flax or enzyme supplementation was minimal on the fatty acids measured in breast muscle except for total n-6 fatty acids which was higher (P < 0.05) in Flax15 when compared to Flax10. In thigh muscle, stearic acid, arachidonic acid, and total n-6 fatty acids were higher in birds fed Flax15 vs. Flax10. Feeding Flax15 led to a reduction in dry matter of excreta when compared to Flax10 (P < 0.05). There were no differences in BW, average daily gain, or feed consumption during the starter or grower phase due to flax level or enzyme addition (P > 0.05).