Introduction: Animal studies reveal that conjugated linoleic acid (CLA) alters body composition, but few studies have examined the effects of CLA supplementation on body composition and leptin concentration in post menopausal women. Materials and Methods: In the present study, A randomized, double blind, placebo-controlled trial was performed to examine the changes in body composition and leptin concentration following 12 week supplementation of either 4 capsules of CLAG80 containing 3.2g CLA (50: 50 ratios of cis-9, trans-11 and trans-10, cis-12 isomers) or 4 placebo capsules (high oleic sunflower) in post-menopausal women. Seventy-six healthy post-menopausal women were randomized to receive placebo or 3.2g CLA for 12 weeks. Dual-Energy X-Ray Absorptiometry was used to measure body composition at baseline and after 12 weeks. Blood samples were collected after 10-12 hours fasting before and after intervention in order to determine leptin levels. Subjects completed 3 day dietary records during the trial, at week 0 (baseline), and at weeks 6 and 12. These dietary records were coded by the same dietitian, and analyzed using Food Processor II. Anthropometric measurements were done according to standard methods. Results: Baseline data for time since menopausal age, BMI, fat mass, lean mass, waist circumference, physical activity and systolic and diastolic pressure were similar in both groups. Dietary CLA in the CLA and placebo groups were 104.5±43.2 mg and 99.5 ±38.2 mg respectively. Although lean body mass increased by 0.87 kg in the CLA group (p<0.00) after 12 weeks of intervention, leptin concentration did not change in either group. Conclusion: Conjugated Linoleic Acid supplementation improves loss of skeletal muscle in postmenopausal women.