In this study, we have examined the antioxidant activity and total phenolic content of different extracts (including water, methanol, water : methanol and acetone) of Nerium oleander L. grown in the north of Iran by employing various in-vitro assay, i.e. DPPH free radical scavenging, reducing power and total antioxidant capacity through the Mo (VI) reduction. The extracts showed different levels of efficacy in each assay in a dose- dependent manner. Methanolic and aqueous methanolic extracts with the highest amount of total phenolic (by using the Folin-Ciocalteu phenol reagent method), were the most potent antioxidant in all of the assays that were used. According to the results of present study, Nerium oleander L. flowers were found to serve as a potential source of natural antioxidants.