Background: Today, the use of antioxidants, especially natural antioxidants, to prevent oxidation is preferred because it has neither the harmful effects of synthetic antioxidants nor requires complex process. In this study, the bioactive compounds and antioxidant properties of mangrove (Avicenna marinia) ethanolic extract were evaluated.Methods: The antioxidant activity of the extract was investigated by DPPH˙, β-carotene bleaching and ferric reducing power tests. The total phenolic content of the Avicenna marinia extract was obtained by Folin-Ciocalteau colorimetric method. Data analysis was performed using SAS, and comparison of average data was done using Least Significant Difference (LSD) at a level of 0.01. Results: The results showed that total phenolic content of the extract was 18.721± 0.14 mg of gallic acid per gram of extract, and in the DPPH radical test, EC50 index was 9650 ± 342 ppm. The major compounds of leaf extract of Avicennia marina were cryptomeridiol (7.82%) and cedrondiol (7.13%). Conclusion: Avicenna marinia leaf extract as natural antioxidants can replace synthetic antioxidants.