A study was conducted to know the effects of dietary oil sources rich in n-6 and n-3 FA on nutrient intake, digestibility, rumen microbial population and fatty acid (FA) profile in sheep. Four pre-pubertal female sheep (48.03 ± 3.69 kg) were housed individually in digestion crates in 4 × 4 Latin square design. Timothy hay and concentrate mixture (3:7 ratio) was the basal diet which was supplied at 2% of live weight on DM basis. Treatments were control (CON), corn oil (CO: n-6), linseed oil (LSO; n-3), and calcium salt of FA (Ca-Salt; protected n-6). Oil sources were pre-mixed with concentrate at 3% of fresh weight. Each period consisted with 10 d of adaptation and 5 d of sample collection. The orts, feces and urine were collected daily before morning feed during the collection period. Blood sample was collected on collection d 4 after 1 h of morning feed, while rumen fluid sample was collected on d 5 at 3 h after morning feed by stomach tube. Data were analyzed using the GLM procedure of SAS. It was observed that intake and digestibility of nutrients were not affected by the supplementing oil sources (P > 0.05). Real Time PCR revealed no differences in DNA concentration of methanogenic archaea (P = 0.047), Fibrobacter succinogens (P = 0.307) and Ruminococcus falvefacience (P = 0.327) among treatments. On the other hand, DNA concentration of rumen ciliate (Entodinium) was reduced (P = 0.018) by Ca-Salt, while Ruminococcus albus was reduced (P = 0.028) by LSO compared with the others. The ruminal concentration of C18:0 was highest (P = 0.012), but C16:0 (P = 0.001) and C16:1n-9 (P = 0.018) were lowest in LSO treatment. Other major 18-carbon FAs remained unaffected (P > 0.05) in rumen contents. Plasma FA profile showed that, not only C18:3n-3 (P < 0.001), but also C20:5n-3 (P = 0.033) were increased by LSO supplementation. Consequently, n-6 to n-3 FA ratio (P = 0.007) was decreased by LSO treatment. Results indicated that, increased concentration of n-3 FA and decreased n-6 to n-3 FA ratio in plasma can be achieved by supplementing linseed oil in ruminant’s diet without affecting intake and digestibility of nutrients.