The objective of the study was to determine if flaxseed treated with a formaldehyde-free process could increase n-3 fatty acid (FA) concentrations in lamb and steer muscle. Twenty-four lambs (initial BW 43.8 ± 4.4 kg) were randomly divided into 4 groups for a 90-d trial. One treatment group (FLX) was fed 136 g/d of nontreated ground flaxseed; another treatment group (FLXT1) was fed 136 g/d of flaxseed treated to protect a-linolenic acid (ALA) from microbial hydrogenation; a third treatment group (FLXT2) was fed 136 g/d of a second treated flaxseed; and a fourth treatment group (CNTL) was fed corn and soybean meal with similar CP and DE levels as the other treatments. Intake of treated flaxseed raised plasma triacylglycerol concentrations of ALA more (P < 0.01) than intake of nontreated flaxseed did, but there was no difference (P = 0.65) in ALA increase between FLXT1 and FLXT2. Intake of treated flaxseed increased (P ≤ 0.05) muscle phospholipid ALA and eicosapentaenoic acid concentrations more than nontreated flaxseed did. There were no differences in muscle phospholipid n-3 concentrations between FLXT1 and FLXT2. Ten yearling steers (initial BW 437 ± 18 kg) were randomly divided into 2 groups. One group was fed ground flaxseed (0.05% of steer BW/d; FLX; n = 5) and a second group was fed treated flaxseed at the same rate (FLXT; n = 5). The 175-d trial was divided into 2 periods: high roughage, low concentrate period followed by high concentrate, low roughage period. Steers were fed rations that were formulated to be isonitrogenous, isocaloric, and isolipidic. There was no difference (P = 0.37) in increase of ALA in blood plasma of FLX and FLXT groups by the end of the first period. However, FLXT had 16% greater (P = 0.003) concentration of ALA in their plasma during the second period. Muscle phospholipid n-3 FA were not greater (P ≥ 0.55) for steers in the FLXT group. Intake of treated flaxseed raised n-3 concentrations in blood and muscle of sheep, and in blood of cattle but did not raise n-3 FA concentrations in muscle of steers. Supplementing the diets of forage-fed lambs with flaxseed treated to reduce hydrogenation of ALA by ruminal microbes can increase concentrations of n-3 FA in the muscle of lambs.