SUMMARY: Presence of various anti-nutritional factors such as mucilage, linatine, cyanogenic glycosides, and trypsin inhibitors in linseed has confined its usage as broiler feed ingredient. The objective of this study was to determine the effect of linseed, after a high-temperature, high-pressure expansion processing, on dietary anti-nutritional factors and nutrient molecular features. Further, an experiment was carried out in a completely randomized design with chicks fed either a control corn–soy diet or graded levels of expanded linseed (EL; 67, 135, and 203 g/kg). Each diet was fed to 8 groups of 15 chicks. Expansion of linseed increased live weight (LW) and reduced feed conversion ratio (FCR; g feed/g LW) considerably. EL incorporation in the diet of chicks increased digestive α-amylase, lipase, trypsin, and total alkaline protease activity. Incorporation of EL in the diet increased villi height and decreased crypt depth. Abdominal fat increased and pancreas weight decreased by inclusion of EL in diets. Gizzard and jejunum pH increased and duodenum pH decreased in chicks fed diets containing EL. The Fourier-transformed infrared spectroscopy showed only reduction in lipid to carbohydrates ratio in molecular structures. Positive correlation was found between FCR and α-helix to ß-sheet ratio and carbohydrate-to-protein ratio. Increased ß-sheet height reduced lipase activity, whereas an increased α-helix to ß-sheet ratio increased lipase activity. The outcome of this study was that expansion was effective for improving the nutritional value of linseed for broiler chicks.