Background: Use of antioxidants is a means of reducing rancidity of fats and oils in food stuffs. The commercial synthetic antioxidants in food industry have been suspected to cause negative health effects. Therefore as alternatives, there is a strong need in finding new effective and safe antioxidants from natural sources to prevent deterioration of foods, drugs and cosmetics. Objectives: In order to investigate the antioxidant activity from natural sources as alternatives of commercial antioxidants, the antioxidant activity of the extracts of leaves and fruits of six different species of Iranian common conifers: Cupressus arizonica, Pinus halepensis, Pinus nigra, Pinus brutia var. elderica, Pinus wallichiana and Cedrus deodara were investigated in the current study. Materials and Methods:The leaves and fruits of these plants were collected from different areas of the country. Methanol extracts of leaves and fruits of Iranian common conifers (six species) were prepared. Antioxidant activity of the samples was measured using ferric thiocyante (FTC) and thiobarbituric acid (TBA) tests. Results:The results of the study, using the two methods, showed that all methanol extracts of leaves and fruits of the six species possessed antioxidant activity. The antioxidant activity of the samples was compared with the antioxidant activities of butylatedhydroxytoluene (BHT), as a synthetic antioxidant and α-tocopherol as a natural antioxidant. Methanol extractions of Pinus spp. leaves and fruits showed the highest antioxidant activity (quite higher than α-tocopherol). Among the extracts examined, the leaves of P. halpensis methanol extract showed the lowest activity. Conclusions: At this stage it can be concluded that methanol extracts of these plants can be considered as strong antioxidant agents. However more investigation is necessary in order to evaluate the antioxidant activity of the components separate from each extracted sample using several different antioxidant methods.