This study aims to investigate the chemical composition of essential oils (EO) extracted from the aerial part of Thymus vulgaris L. and to evaluate its antifungal activity on the apple scab pathogen (Venturia ineaqualis L). Chemical analysis of this EO showed the presence of 30 compounds which represent about 99.07% of the overall component which is formed principaly by linalool (36.41%), followed by Terpinen-4-ol (10.51%) and β-myrcene (7.5%). Other constituents are identified moderatly [para-Cymene (6.6%); γ-terpinene (6.11%)] and lowly [carvacrol (0.75%)] with thymol completely absent. The evaluation of antifungal activity of thyme EO on the growth of Venturia ineaqualis mycelium, was marked by decreasing number of filaments of the fungal colony depending increasing doses where the minimum inhibitory concentration is 300µl/ml and the minimum fungal concentration is 600µl/ml for which no growth is detected. In spite of the absence of thymol and the rather low content of carvacrol, known for their high toxicity, thyme EO from the Seraidi region was very effective and revealed a very powerful activity against V.ineaqualis which is probably due to the presence high levels of monoterpenes (36.96%) and oxygenated monoterpenes (55.51%) associated with other components which work in synergy even at low doses.