Objective: To assess the effect of flaxseed supplementation on metabolic profile, endocrine concentrations, non-esterified fatty acids (NEFA), body composition variables, and reproductive performance of sows.Methods: All the 21 crossbred Large White Yorkshire sows were considered in the study period starting at day 1 of current farrowing when the feeding of specific supplemental ration was started until the day of subsequent farrowing (days 150-155) and were equally allocated into three groups. Group 1 served as the control group and followed their normal feeding schedule. Group 2 and group 3, in addition to their normal feeding schedule, were supplemented with flaxseed at a rate of 0.5％ and 1.0％ of the dry matter, respectively. Blood samples were collected 15 days prior to farrowing, on the day of farrowing (day 0), at weekly intervals until day 28 of lactation and at monthly intervals during gestation to harvest the plasma. Plasma was used to assess the metabolic and endocrine status of sows. Body weight of each sow and individual birth weight of all piglets born were measured. Results: Flaxseed supplementation led to decrease in plasma cholesterol and triglyceride levels in the supplemented groups than in the control group (P<0.05). Plasma estradiol-17β level was higher in group 2 than that in group 1 and 3 on day 90 of the gestation period (P<0.05). The mean plasma level of insulin-like growth factor 1 was higher in group 3 than that in group 1 and 2 both in late lactation (day 28) as well as in early gestation (day 30) (P<0.05). Plasma NEFA and weight gain were greater in sows of group 2 and 3 compared to those fed with the normal control diets (P0.05). Conclusions: Flaxseed improves endocrine profiles, NEFA concentrations and body weight, resulting in better pregnancy rate and litter size.