Stabilization of biodiesel against oxidation is known to be an important task for its storage and effective use. One of the convenient approaches to solve this task is the introduction of antioxidant additives. Since no particular inhibitor is found to be useful for every biodiesel type, it is of current importance to search for and to study novel efficient antioxidant additives. The antioxidant-rich extracts from plants of various origin may be a promising source for such kind of additives. The aim of this work was to study the extracts from the leaves of thirteen plants and from the eight samples of vegetable oil production wastes as potential additives for the improvement of biodiesel stability against oxidation. Composition and antioxidant properties of the extracts were studied by means of HPLC, MALDI MS, Folin-Ciocalteu and DPPH methods. All the extracts were found to contain large amount of phenolic compounds, with the nature and quantity of the antioxidants being dependent on the raw material used for the extract preparation. Hydroxycinnamic acids and quercetin glicosides were the main constituents of the majority of the extracts, while hydroxybenzoic acids and catechin derivatives prevailed in several extracts. In spite of significant distinctions in phenols content, all the extracts were found to possess very high antioxidant activity in both Folin-Ciocalteu and DPPH assays. The overall amount of phenolic compounds in the extracts was up to 350 mg/L. Five extracts with the highest antioxidant ability was also tested as an additive to stabilize the biodiesel against oxidation. The biodiesel stability was studied according to accelerated procedure at 43C for 12 weeks (that is equivalent of 12 months of diesel maintenance at room temperature), with the changes in the acid value of the samples being the criteria of fuel oxidation. The results showed that the extracts can provide the deceleration of biodiesel oxidation by 5-25%, as determined by comparison of acid number for the diesel samples with and without antioxidant additives. The HPLC and LDI MS studies have shown that after maintaining two biodiesel samples for 12 weeks at 43C a set of the compounds related to the products of original fat acid esters oxidation are formed. The oxidation of original esters in biodiesels was found to be inhibited by up to 15% upon extracts addition. These data are in agreement with the results of biodiesel oxidation test and confirm the stabilizing effect of the plant extract components. Among all the extracts studied, the ones from Silybum and Camellia japonica L. were found to provide the greatest inhibition of biodiesel oxidation; these extracts can be considered as a promising stabilizing additive to reduce the biodiesel oxidation. Acknowledgement. This work was financially supported by National Research Foundation of Ukraine (Project No2020.01/0136 «Efficient use of renewable plant resources and photocatalytic conversion of biomass as eco-innovative approaches for environmental protection and human biosafety»).