The present work aimed to carry out the phytochemical analysis and antioxidant activity of hydro-methanolic, ethyl acetate and butanolic extracts of Dianthus sylvestris subsp, aristidis (Batt,) Greuter & Burdet leaves. Phenolics, flavonoids and flavonols contents were measured by the Folin-Ciocalteu reagent and the aluminum chloride (AlCl3) method respectively. Phytochemical analysis was determined by using LC-ESI-MS/MS method. Antioxidant activity, in vitro, was evaluated by six different assays including: DPPH scavenging, ABTS cation radical, Ferrous ions chelating, Phenanthroline, Reducing power and Silver nanoparticle. The findings showed that the butanolic extract was found to be higher in phenolics and flavonoids contents (121.45 ± 1.87 μg GAE/mg extract and 57.09±0.14 μg QE/mg extract respectively). While ethyl acetate extract was found to be higher in falvonols contents (41.90±0.98µg QE/mg extract). The LC-ESI-MS/MS analysis of ethyl acetate and butanolic extracts revealed the presence of fifteen compounds among which: four phenolic acids, five flavonoids, one phenolic aldehyde and three vitamins, with P- coumaric acid, Hesperetin, Vanillin, Ascorbic Acid as major compounds respectively. The butanolic and ethyl acetate extracts exhibited the highest antioxidant activity in Phenanthroline assay (A0,5: 17.75± 0.72 µg/mL and A0.5: 21.02 ± 0.43 µg/mL respectively). On the basis of the significant findings, D. sylvestris subsp, aristidis would be recommended as a new potential source of natural antioxidant for pharmaceutical industries.