Introduction. Hippophae rhamnoides L., the common sea buckthorn, deciduous shrubs in the family Elaeagnaceae. The plant is being used in different parts of the world for its nutritional and medicinal properties.  Aim of the study. The present study focused on the antioxidant activity determination and total phenolic content of leaves (fresh/dried) and fruits (fresh/dried) of Hippophae rhamnoides L. Materials and methods. In vitro antioxidant activity of extracts was assayed by DPPH, ABTS, and Iron chelating activity (ferrozine) tests. Total total phenolic content was determined by using the Folin-Ciocalteu assay.  Results. In all assays, the leaves of H. rhamnoides L. showed higher value of antioxidant activity (fresh: DPPH – IC50=28.88 µg/ml; ABTS – 28.79 µM TE/g dried weight; Iron chelating activity – 33.40 %; dried: DPPH – IC50=25.67µg/ml; ABTS – 29.04 µM TE/g dried weight; Iron chelating activity – 53.06 %) than fruit extracts (fresh: DPPH – IC50=357.97 µg/ml; ABTS –16.44 µM TE/g dried weight; Iron chelating activity – none; dried: DPPH – IC50=689.52 µg/ml; ABTS – 9.03 µM TE/g dried weight; Iron chelating activity – none). The total phenolic contents in the examined leaves and fruits of H. rhamnoides extracts were 2.91 (died) – 4.57 (fresh) and 0.54 (fresh) – 2.30 (dried) mg GAE/g, respectively. Conclusions. H. rhamnoides leaf extracts have shown considerable antioxidant properties. The consumption of this may play a role in preventing several human diseases, which involve the free radicals, such as cancer, cardiovascular disease, and premature aging. Thus, further investigations on the in vivo antioxidant activity and other antioxidant mechanisms are warranted.