We hypothesized that supplementation of linseed in a beef cattle fattening diet would increase PUFA concentrations in intramuscular adipose tissue and depress (), (), and () gene expression by decreasing () expression. Conversely, supplemental linseed would upregulate expression of () and () in muscle of Yanbian Yellow steers. Thirty steers were assigned at random to 3 groups of 10 steers fed either the basal diet (corn grain and corn silage-based commercial concentrate [CON]), the CON diet plus 8% whole linseed (WLS; DM basis), or the CON diet plus 8% cracked linseed (CLS; DM basis) for 6 mo. The WLS and CLS supplements did not affect carcass weight, backfat thickness, or marbling scores ( > 0.10) but increased rib eye area and fat color (more yellow; < 0.05). The WLS and CLS diets decreased the proportions of 16:0 and 18:0 and increased the proportions of 18:1-9, 18:3-3, -9, -11 conjugated linoleic acid, total MUFA, and total PUFA in intramuscular, intermuscular, and subcutaneous adipose tissues. The WLS and CLS diets increased and gene expression whereas the supplements depressed , , , and gene expression in longissimus thoracis muscle, relative to CON muscle, consistent with our hypothesis. Because the WLS and CLS treatments did not affect any measure of carcass adiposity, these results indicated that linseed supplements promoted uptake of dietary lipids while concurrently depressing de novo fatty acid biosynthesis in adipose tissue.