The objective of this study was to investigate the effect of planting dates and harvesting at different developmental stages on growth, herb, essential oil content and its composition of Marrubium vulgare grown under Egyptian conditions. Marrubium vulgare seeds were sown in the nursery in three different dates (March 15, April 1, and April 15). After two months, seedlings were transplanted into the field. Plants from each planting date were harvested in three developing stages, i.e. pre-flowering/vegetative stage, full-flowering and post-flowering/seed forming growth. Essential oil was obtained by hydro distillation and essential oil % was expressed as ml 100 g-1 fresh herb. Chemical composition of the essential oil was studied using GC-MS. Marrubium plants cultivated early on March 15th gave the highest plant height, number of branches and fresh and dry weights as compared to the plants that was cultivated later on April 1st or April 15th. On the other hand, harvesting plants at the late flowering stage gave the highest values of these parameters. Regarding the essential oil production, Marrubium plants cultivated early on March 15th or on April 1st and cut at the full flowering stage gave the highest essential oil % and yield as compared to cutting early before flowering stage. About 31 compounds were identified in the essential oil of Marrubium vulgare. Carvacrol (31.80- 40.75%), β-phellandrene (10.99-15.89%) and carvyl acetate (7.57-12.16%) were the major compounds. Whereas β-thujene, α-pinene, 1-octen-3-ol, β-pinene, α-terpinene, 1,8-cineol, linalool, borneol, γ- cadinene and trans-caryophyllene considered minor compounds.